"turtle" --- Turtle graphics
****************************

**Source code:** Lib/turtle.py

======================================================================


Turtle star
^^^^^^^^^^^

Turtle can draw intricate shapes using programs that repeat simple
moves.

[image: A yellow starburst of thin spikes with a red outline, drawn by
turtle.][image]

Imagine a robotic turtle starting at (0, 0) in the x-y plane. After an
"import turtle", give it the command "turtle.forward(15)", and it
moves (on-screen!) 15 pixels in the direction it is facing, drawing a
line as it moves. Give it the command "turtle.right(25)", and it
rotates in-place 25 degrees clockwise.

Turtle graphics is an implementation of the drawing tools introduced
in Logo in 1967. It was created as an educational tool, and its
instant, visible feedback makes it an effective way for learners to
encounter programming concepts. It is also a convenient way to produce
simple graphical output without bringing in external libraries.

This document includes four main sections:

* Tutorial teaches the basics of turtle drawing.

* Reference describes the functions, methods and classes this module
  defines.

* How-to guides detail how to handle specific tasks.

* Explanation provides background on the object-oriented interface.

Note:

  Turtle graphics requires the "tkinter" *optional module*. The
  python.org installers for Windows and macOS include it, but some
  Linux distributions and other platforms may package it separately.
  If "import turtle" fails with an error mentioning "_tkinter", look
  for documentation from your distributor (that is, whoever provided
  Python to you). Check this in advance if you're planning to use
  turtle graphics with a learner.


Tutorial
========

New users should start here. In this tutorial we'll explore some of
the basics of turtle drawing.


Starting a turtle environment
-----------------------------

In a Python shell, import all the objects of the "turtle" module:

   from turtle import *

If you run into a "Standard library module '_tkinter' was not found"
error, you'll have to install the "Tk interface package" on your
system.

Nothing appears yet. To open the turtle window, make the turtle
visible:

   showturtle()

A new window opens, with the turtle in the middle, shown as an arrow
heading East.


Basic drawing
-------------

Send the turtle forward 100 steps:

   forward(100)

You should see a line drawn by the turtle, heading East. Change the
direction of the turtle, so that it turns 120 degrees left (anti-
clockwise):

   left(120)

Let's continue by drawing a triangle:

   forward(100)
   left(120)
   forward(100)

Notice how the turtle, represented by an arrow, points in different
directions as you steer it.

Experiment with those commands, and also with "backward()" and
"right()". Many commands also have shorter aliases, such as "fd()" for
"forward()".


Pen control
~~~~~~~~~~~

Try changing the color - for example, "color('blue')" - and width of
the line - for example, "width(3)" - and then drawing again.

You can also move the turtle around without drawing, by lifting up the
pen: "up()" before moving. To start drawing again, use "down()".


The turtle's position
~~~~~~~~~~~~~~~~~~~~~

Send your turtle back to its starting-point (useful if it has
disappeared off-screen):

   home()

The home position is at the center of the turtle's screen. If you ever
need to know them, get the turtle's x-y coordinates with:

   pos()

Home is at "(0, 0)".

And after a while, it will probably help to clear the window so we can
start anew:

   clearscreen()


Making algorithmic patterns
---------------------------

Using loops, it's possible to build up geometric patterns:

   for steps in range(100):
       for c in ('blue', 'red', 'green'):
           color(c)
           forward(steps)
           right(30)

- which of course, are limited only by the imagination!

Let's draw the star shape at the top of this page. We want red lines,
filled in with yellow:

   color('red')
   fillcolor('yellow')

Just as "up()" and "down()" determine whether lines will be drawn,
filling can be turned on and off:

   begin_fill()

Next we'll create a loop:

   start = pos()

   while True:
       forward(200)
       left(170)
       if distance(start) < 1:
           break

"distance(start) < 1" is a good way to know when the turtle is back at
its start position.

Finally, complete the filling:

   end_fill()

(Note that filling only actually takes place when you give the
"end_fill()" command.)


Reference
=========


Turtle methods and functions
----------------------------

Most of the examples in this section refer to a Turtle instance called
"turtle".


Move and draw
~~~~~~~~~~~~~

turtle.forward(distance)
turtle.fd(distance)

   Parameters:
      **distance** -- a number

   Move the turtle forward by the specified *distance*, in the
   direction the turtle is headed.

      >>> turtle.position()
      (0.00,0.00)
      >>> turtle.forward(25)
      >>> turtle.position()
      (25.00,0.00)
      >>> turtle.forward(-75)
      >>> turtle.position()
      (-50.00,0.00)

turtle.back(distance)
turtle.bk(distance)
turtle.backward(distance)

   Parameters:
      **distance** -- a number

   Move the turtle backward by *distance*, opposite to the direction
   the turtle is headed. The turtle's heading does not change.

      >>> turtle.position()
      (0.00,0.00)
      >>> turtle.backward(30)
      >>> turtle.position()
      (-30.00,0.00)

turtle.right(angle)
turtle.rt(angle)

   Parameters:
      **angle** -- a number

   Turn the turtle right by the specified *angle*. The angle is
   measured in degrees by default; the unit can be changed with
   "degrees()" or "radians()". How the heading is measured depends on
   the turtle mode, see "mode()".

      >>> turtle.heading()
      22.0
      >>> turtle.right(45)
      >>> turtle.heading()
      337.0

turtle.left(angle)
turtle.lt(angle)

   Parameters:
      **angle** -- a number

   Turn the turtle left by the specified *angle*. The angle is
   measured in degrees by default; the unit can be changed with
   "degrees()" or "radians()". How the heading is measured depends on
   the turtle mode, see "mode()".

      >>> turtle.heading()
      22.0
      >>> turtle.left(45)
      >>> turtle.heading()
      67.0

turtle.goto(x, y=None)
turtle.setpos(x, y=None)
turtle.setposition(x, y=None)

   Parameters:
      * **x** -- a number or a pair/vector of numbers

      * **y** -- a number or "None"

   Move the turtle to an absolute position. If *y* is "None", *x* must
   be a pair of coordinates or a "Vec2D", for example as returned by
   "pos()". If the pen is down, a line is drawn. The turtle's heading
   does not change.

      >>> tp = turtle.pos()
      >>> tp
      (0.00,0.00)
      >>> turtle.goto(60,30)
      >>> turtle.pos()
      (60.00,30.00)
      >>> turtle.goto((20,80))
      >>> turtle.pos()
      (20.00,80.00)
      >>> turtle.goto(tp)
      >>> turtle.pos()
      (0.00,0.00)

turtle.teleport(x=None, y=None, *, fill_gap=False)

   Parameters:
      * **x** -- a number or "None"

      * **y** -- a number or "None"

      * **fill_gap** -- a boolean

   Teleport, or instantly move, the turtle to an absolute position.
   Unlike "goto()", no line is drawn. If *x* or *y* is not given, that
   coordinate is kept as it is. The turtle's heading does not change.

   If the turtle is filling a shape, the shape drawn so far is
   finished and filled before teleporting, and filling starts again at
   the new position. Pass "fill_gap=True" to keep filling one shape
   instead. The teleport then counts as an edge of the shape, as it
   would with "goto()".

      >>> tp = turtle.pos()
      >>> tp
      (0.00,0.00)
      >>> turtle.teleport(60)
      >>> turtle.pos()
      (60.00,0.00)
      >>> turtle.teleport(y=10)
      >>> turtle.pos()
      (60.00,10.00)
      >>> turtle.teleport(20, 30)
      >>> turtle.pos()
      (20.00,30.00)

   Added in version 3.12.

turtle.setx(x)

   Parameters:
      **x** -- a number

   Set the turtle's x coordinate to *x*. The y coordinate is
   unchanged.

      >>> turtle.position()
      (0.00,240.00)
      >>> turtle.setx(10)
      >>> turtle.position()
      (10.00,240.00)

turtle.sety(y)

   Parameters:
      **y** -- a number

   Set the turtle's y coordinate to *y*. The x coordinate is
   unchanged.

      >>> turtle.position()
      (0.00,40.00)
      >>> turtle.sety(-10)
      >>> turtle.position()
      (0.00,-10.00)

turtle.setheading(to_angle)
turtle.seth(to_angle)

   Parameters:
      **to_angle** -- a number

   Set the turtle's heading to *to_angle*. Here are some common
   directions in degrees:

   +---------------------+----------------------+
   | standard mode       | logo mode            |
   |=====================|======================|
   | 0 - east            | 0 - north            |
   +---------------------+----------------------+
   | 90 - north          | 90 - east            |
   +---------------------+----------------------+
   | 180 - west          | 180 - south          |
   +---------------------+----------------------+
   | 270 - south         | 270 - west           |
   +---------------------+----------------------+

      >>> turtle.setheading(90)
      >>> turtle.heading()
      90.0

turtle.home()

   Move the turtle to the origin, coordinates (0,0). The turtle's
   heading is set to its start orientation, which depends on the
   turtle mode, see "mode()".

      >>> turtle.heading()
      90.0
      >>> turtle.position()
      (0.00,-10.00)
      >>> turtle.home()
      >>> turtle.position()
      (0.00,0.00)
      >>> turtle.heading()
      0.0

turtle.circle(radius, extent=None, steps=None)

   Parameters:
      * **radius** -- a number

      * **extent** -- a number or "None"

      * **steps** -- an integer or "None"

   Draw a circle with the given *radius*. The center is *radius* units
   left of the turtle; *extent*, an angle, determines which part of
   the circle is drawn. If *extent* is not given, draw the entire
   circle. If *extent* is not a full circle, one endpoint of the arc
   is the current pen position. Draw the arc in counterclockwise
   direction if *radius* is positive, otherwise in clockwise
   direction. Finally, the turtle's heading is changed by *extent*.

   As the circle is approximated by an inscribed regular polygon,
   *steps* determines the number of steps to use. If not given, it
   will be calculated automatically. May be used to draw regular
   polygons.

      >>> turtle.home()
      >>> turtle.position()
      (0.00,0.00)
      >>> turtle.heading()
      0.0
      >>> turtle.circle(50)
      >>> turtle.position()
      (-0.00,0.00)
      >>> turtle.heading()
      0.0
      >>> turtle.circle(120, 180)  # draw a semicircle
      >>> turtle.position()
      (0.00,240.00)
      >>> turtle.heading()
      180.0

turtle.dot()
turtle.dot(size)
turtle.dot(color, /)
turtle.dot(size, color, /)
turtle.dot(size, r, g, b, /)

   Parameters:
      * **size** -- a positive integer or "None"

      * **color** -- a colorstring or a numeric color tuple

   Draw a circular dot with diameter *size*, using *color*. If *size*
   is not given, the larger of "pensize + 4" and "2 * pensize" is
   used. If *color* is not given, the current pencolor is used.

      >>> turtle.home()
      >>> turtle.dot()
      >>> turtle.fd(50); turtle.dot(20, "blue"); turtle.fd(50)
      >>> turtle.position()
      (100.00,-0.00)
      >>> turtle.heading()
      0.0

turtle.stamp()

   Stamp a copy of the turtle shape onto the canvas and return its id.
   The stamp is placed at the current turtle position. The returned id
   can be used to delete the stamp with "clearstamp()".

      >>> turtle.color("blue")
      >>> stamp_id = turtle.stamp()
      >>> turtle.fd(50)

turtle.clearstamp(stampid)

   Parameters:
      **stampid** -- an integer

   Delete the stamp with the given *stampid*. *stampid* must be the
   return value of a previous "stamp()" call.

      >>> turtle.position()
      (150.00,-0.00)
      >>> turtle.color("blue")
      >>> astamp = turtle.stamp()
      >>> turtle.fd(50)
      >>> turtle.position()
      (200.00,-0.00)
      >>> turtle.clearstamp(astamp)
      >>> turtle.position()
      (200.00,-0.00)

turtle.clearstamps(n=None)

   Parameters:
      **n** -- an integer or "None"

   Delete all or the first or last *n* of the turtle's stamps. If *n*
   is not given, delete all stamps. If *n* is positive, delete the
   first *n* stamps. If *n* is negative, delete the last *n* stamps,
   so -2 deletes the last two.

      >>> for i in range(8):
      ...     unused_stamp_id = turtle.stamp()
      ...     turtle.fd(30)
      >>> turtle.clearstamps(2)
      >>> turtle.clearstamps(-2)
      >>> turtle.clearstamps()

turtle.undo()

   Undo (repeatedly) the last turtle action(s).  Number of available
   undo actions is determined by the size of the undobuffer.

      >>> for i in range(4):
      ...     turtle.fd(50); turtle.lt(80)
      ...
      >>> for i in range(8):
      ...     turtle.undo()

turtle.speed(speed=None)

   Parameters:
      **speed** -- an integer, a string or "None"

   Return or set the turtle's speed. If *speed* is not given, return
   the current speed. Otherwise set the turtle's speed to an integer
   from 0 to 10. If *speed* is a number greater than 10 or smaller
   than 0.5, the speed is set to 0. You can also use these names
   instead of numbers:

   * "fastest": 0

   * "fast": 10

   * "normal": 6

   * "slow": 3

   * "slowest": 1

   Speeds from 1 to 10 give increasingly faster animation of line
   drawing and turtle turning. A speed of 0 means that no animation
   takes place: "forward()" and "back()" make the turtle jump, and
   likewise "left()" and "right()" make the turtle turn instantly.

      >>> turtle.speed()
      3
      >>> turtle.speed('normal')
      >>> turtle.speed()
      6
      >>> turtle.speed(9)
      >>> turtle.speed()
      9


Tell Turtle's state
~~~~~~~~~~~~~~~~~~~

turtle.position()
turtle.pos()

   Return the turtle's current location (x,y) as a "Vec2D" vector.

      >>> turtle.pos()
      (440.00,-0.00)

turtle.towards(x, y=None)

   Parameters:
      * **x** -- a number or a pair/vector of numbers or a turtle
        instance

      * **y** -- a number if *x* is a number, else "None"

   Return the angle of the line from the turtle's position to (x,y).
   If *y* is "None", *x* must be a pair of coordinates, a "Vec2D", for
   example as returned by "pos()", or another turtle. The angle is
   measured from the turtle's start orientation, which depends on the
   turtle mode, see "mode()".

      >>> turtle.goto(10, 10)
      >>> turtle.towards(0,0)
      225.0

turtle.xcor()

   Return the turtle's x coordinate.

      >>> turtle.home()
      >>> turtle.left(50)
      >>> turtle.forward(100)
      >>> turtle.pos()
      (64.28,76.60)
      >>> print(round(turtle.xcor(), 5))
      64.27876

turtle.ycor()

   Return the turtle's y coordinate.

      >>> turtle.home()
      >>> turtle.left(60)
      >>> turtle.forward(100)
      >>> print(turtle.pos())
      (50.00,86.60)
      >>> print(round(turtle.ycor(), 5))
      86.60254

turtle.heading()

   Return the turtle's current heading. The value depends on the
   turtle mode, see "mode()".

      >>> turtle.home()
      >>> turtle.left(67)
      >>> turtle.heading()
      67.0

turtle.distance(x, y=None)

   Parameters:
      * **x** -- a number or a pair/vector of numbers or a turtle
        instance

      * **y** -- a number if *x* is a number, else "None"

   Return the distance from the turtle to (x,y) in turtle step units.
   If *y* is "None", *x* must be a pair of coordinates, a "Vec2D", for
   example as returned by "pos()", or another turtle.

      >>> turtle.home()
      >>> turtle.distance(30,40)
      50.0
      >>> turtle.distance((30,40))
      50.0
      >>> joe = Turtle()
      >>> joe.forward(77)
      >>> turtle.distance(joe)
      77.0


Settings for measurement
~~~~~~~~~~~~~~~~~~~~~~~~

turtle.degrees(fullcircle=360.0)

   Parameters:
      **fullcircle** -- a number

   Set the angle measurement units to degrees. The number of degrees
   in a full circle is set to *fullcircle*, which defaults to 360.

      >>> turtle.home()
      >>> turtle.left(90)
      >>> turtle.heading()
      90.0

      >>> # Change angle measurement unit to grad (also known as gon,
      >>> # grade, or gradian and equals 1/100-th of the right angle.)
      >>> turtle.degrees(400.0)
      >>> turtle.heading()
      100.0
      >>> turtle.degrees(360)
      >>> turtle.heading()
      90.0

turtle.radians()

   Set the angle measurement units to radians.  Equivalent to
   "degrees(2 * math.pi)".

      >>> turtle.home()
      >>> turtle.left(90)
      >>> turtle.heading()
      90.0
      >>> turtle.radians()
      >>> turtle.heading()
      1.5707963267948966


Pen control
~~~~~~~~~~~


Drawing state
"""""""""""""

turtle.pendown()
turtle.pd()
turtle.down()

   Lower the pen. The turtle draws a line when it moves.

turtle.penup()
turtle.pu()
turtle.up()

   Lift the pen. The turtle does not draw when it moves.

turtle.pensize(width=None)
turtle.width(width=None)

   Parameters:
      **width** -- a positive number or "None"

   Return or set the line thickness. If *width* is not given, return
   the current pensize. If resizemode is set to "auto" and the turtle
   shape is a polygon, that polygon is drawn with the same line
   thickness.

      >>> turtle.pensize()
      1
      >>> turtle.pensize(10)   # from here on lines of width 10 are drawn

turtle.pen(pen=None, **pendict)

   Parameters:
      * **pen** -- a dictionary or "None"

      * **pendict** -- keyword arguments with the keys below

   Return or set the pen's attributes. The attributes are returned as
   a dictionary with the following keys and values:

   * "shown": "True" or "False"

   * "pendown": "True" or "False"

   * "pencolor": a color string or a color tuple

   * "fillcolor": a color string or a color tuple

   * "pensize": a positive number

   * "speed": a number from 0 to 10

   * "resizemode": "auto", "user" or "noresize"

   * "stretchfactor": a pair of positive numbers

   * "shearfactor": a number

   * "outline": a positive number

   * "tilt": a number

   Such a dictionary can be passed as *pen* to restore a former pen
   state. The attributes can also be given as keyword arguments, which
   can be used to set several of them in one statement.

      >>> turtle.pen(fillcolor="black", pencolor="red", pensize=10)
      >>> turtle.pen()
      {'shown': True, 'pendown': True, 'pencolor': 'red', 'fillcolor': 'black',
       'pensize': 10, 'speed': 9, 'resizemode': 'noresize',
       'stretchfactor': (1.0, 1.0), 'shearfactor': 0.0, 'outline': 1,
       'tilt': 0.0}
      >>> penstate = turtle.pen()
      >>> turtle.color("yellow", "")
      >>> turtle.penup()
      >>> turtle.pen()["pencolor"]
      'yellow'
      >>> # restore the saved pen state, but with a green fill
      >>> turtle.pen(penstate, fillcolor="green")
      >>> turtle.pen()["pencolor"]
      'red'
      >>> turtle.pen()["fillcolor"]
      'green'

turtle.isdown()

   Return "True" if the pen is down, "False" if it's up.

      >>> turtle.penup()
      >>> turtle.isdown()
      False
      >>> turtle.pendown()
      >>> turtle.isdown()
      True


Color control
"""""""""""""

turtle.pencolor()
turtle.pencolor(color, /)
turtle.pencolor(r, g, b, /)

   Return or set the pencolor.

   Four input formats are allowed:

   "pencolor()"
      Return the current pencolor as color specification string or as
      a tuple (see example).  May be used as input to another
      "color()", "pencolor()", "fillcolor()" or "bgcolor()" call.

   "pencolor(colorstring)"
      Set the pencolor to *colorstring*, which is a Tk color
      specification string, such as ""red"", ""yellow"", or
      ""#33cc8c"".

   "pencolor((r, g, b))"
      Set the pencolor to the RGB color represented by the tuple of
      *r*, *g*, and *b*. Each of *r*, *g*, and *b* must be between 0
      and colormode, where colormode is either 1.0 or 255 (see
      "colormode()").

   "pencolor(r, g, b)"
      Set the pencolor to the RGB color represented by *r*, *g*, and
      *b*. Each of *r*, *g*, and *b* must be between 0 and colormode.

   If the turtle shape is a polygon, the outline of that polygon is
   drawn with the newly set pencolor.

      >>> colormode()
      1.0
      >>> turtle.pencolor()
      'red'
      >>> turtle.pencolor("brown")
      >>> turtle.pencolor()
      'brown'
      >>> tup = (0.2, 0.8, 0.55)
      >>> turtle.pencolor(tup)
      >>> turtle.pencolor()
      (0.2, 0.8, 0.5490196078431373)
      >>> colormode(255)
      >>> turtle.pencolor()
      (51.0, 204.0, 140.0)
      >>> turtle.pencolor('#32c18f')
      >>> turtle.pencolor()
      (50.0, 193.0, 143.0)

turtle.fillcolor()
turtle.fillcolor(color, /)
turtle.fillcolor(r, g, b, /)

   Return or set the fillcolor.

   Four input formats are allowed:

   "fillcolor()"
      Return the current fillcolor as color specification string,
      possibly in tuple format (see example).  May be used as input to
      another "color()", "pencolor()", "fillcolor()" or "bgcolor()"
      call.

   "fillcolor(colorstring)"
      Set the fillcolor to *colorstring*, which is a Tk color
      specification string, such as ""red"", ""yellow"", or
      ""#33cc8c"".

   "fillcolor((r, g, b))"
      Set the fillcolor to the RGB color represented by the tuple of
      *r*, *g*, and *b*. Each of *r*, *g*, and *b* must be between 0
      and colormode, where colormode is either 1.0 or 255 (see
      "colormode()").

   "fillcolor(r, g, b)"
      Set the fillcolor to the RGB color represented by *r*, *g*, and
      *b*. Each of *r*, *g*, and *b* must be between 0 and colormode.

   If the turtle shape is a polygon, the interior of that polygon is
   drawn with the newly set fillcolor.

      >>> turtle.fillcolor("violet")
      >>> turtle.fillcolor()
      'violet'
      >>> turtle.pencolor()
      (50.0, 193.0, 143.0)
      >>> turtle.fillcolor((50, 193, 143))  # Integers, not floats
      >>> turtle.fillcolor()
      (50.0, 193.0, 143.0)
      >>> turtle.fillcolor('#ffffff')
      >>> turtle.fillcolor()
      (255.0, 255.0, 255.0)

turtle.color()
turtle.color(color, /)
turtle.color(r, g, b, /)
turtle.color(pencolor, fillcolor, /)

   Return or set the pencolor and fillcolor.

   Several input formats are allowed. They use 0 to 3 arguments as
   follows:

   "color()"
      Return the current pencolor and the current fillcolor as a pair
      of color specification strings or tuples as returned by
      "pencolor()" and "fillcolor()".

   "color(colorstring)", "color((r,g,b))", "color(r,g,b)"
      Inputs as in "pencolor()". Set both the pencolor and the
      fillcolor to the given value.

   "color(colorstring1, colorstring2)", "color((r1,g1,b1),
   (r2,g2,b2))"
      Equivalent to "pencolor(colorstring1)" and
      "fillcolor(colorstring2)" and analogously if the other input
      format is used.

   If the turtle shape is a polygon, the outline and interior of that
   polygon are drawn with the newly set colors.

      >>> turtle.color("red", "green")
      >>> turtle.color()
      ('red', 'green')
      >>> color("#285078", "#a0c8f0")
      >>> color()
      ((40.0, 80.0, 120.0), (160.0, 200.0, 240.0))

See also: Screen method "colormode()".


Filling
"""""""

turtle.filling()

   Return "True" if the turtle is filling, "False" otherwise.

      >>> turtle.begin_fill()
      >>> if turtle.filling():
      ...    turtle.pensize(5)
      ... else:
      ...    turtle.pensize(3)

turtle.fill()

   Fill the shape drawn in the "with" block.

      >>> turtle.color("black", "red")
      >>> with turtle.fill():
      ...     turtle.circle(80)

   "fill()" is a *context manager*, so using it is the same as calling
   "begin_fill()" before the block and "end_fill()" after it:

      >>> turtle.color("black", "red")
      >>> turtle.begin_fill()
      >>> turtle.circle(80)
      >>> turtle.end_fill()

   Added in version 3.14.

turtle.begin_fill()

   Call just before drawing a shape to be filled. The shape is filled
   by the next call to "end_fill()".

turtle.end_fill()

   Fill the shape drawn after the last call to "begin_fill()".

   If the shape crosses itself or several shapes overlap, whether the
   overlapping parts are filled depends on the operating system, the
   type of overlap and how many there are. For example, the turtle
   star above may be either all yellow or have some white regions.

      >>> turtle.color("black", "red")
      >>> turtle.begin_fill()
      >>> turtle.circle(80)
      >>> turtle.end_fill()


More drawing control
""""""""""""""""""""

turtle.reset()

   Delete the turtle's drawings and re-center the turtle. The turtle's
   settings are restored to their default values.

      >>> turtle.goto(0,-22)
      >>> turtle.left(100)
      >>> turtle.position()
      (0.00,-22.00)
      >>> turtle.heading()
      100.0
      >>> turtle.reset()
      >>> turtle.position()
      (0.00,0.00)
      >>> turtle.heading()
      0.0

turtle.clear()

   Delete the turtle's drawings from the screen. The state and
   position of the turtle as well as the drawings of other turtles are
   not affected.

turtle.write(arg, move=False, align='left', font=('Arial', 8, 'normal'))

   Parameters:
      * **arg** -- an object

      * **move** -- a boolean

      * **align** -- a string

      * **font** -- a tuple of a string, an integer and a string

   Write text at the current turtle position. The text is the string
   representation of *arg*. *align* is one of the strings "left",
   "center" or "right" and says how the text is placed relative to the
   turtle position. *font* is a triple of font name, font size and
   font type. If *move* is "True", the pen is moved to the bottom-
   right corner of the text.

      >>> turtle.write("Home = ", True, align="center")
      >>> turtle.write((0,0), True)


Turtle state
~~~~~~~~~~~~


Visibility
""""""""""

turtle.hideturtle()
turtle.ht()

   Make the turtle invisible. If the pen is down, movement still
   draws.

turtle.showturtle()
turtle.st()

   Make the turtle visible.

turtle.isvisible()

   Return "True" if the turtle is visible, "False" if it's hidden.

      >>> turtle.hideturtle()
      >>> turtle.isvisible()
      False
      >>> turtle.showturtle()
      >>> turtle.isvisible()
      True


Appearance
""""""""""

turtle.shape(name=None)

   Parameters:
      **name** -- a string or "None"

   Set the turtle shape to the named shape. If *name* is not given,
   return the name of the current shape. The shape must exist in the
   "TurtleScreen"'s shape dictionary. Initially there are the
   following shapes: "arrow", "turtle", "circle", "square", "triangle"
   and "classic". To add shapes, see the "Screen" method
   "register_shape()".

      >>> turtle.shape()
      'classic'
      >>> turtle.shape("turtle")
      >>> turtle.shape()
      'turtle'

turtle.resizemode(rmode=None)

   Parameters:
      **rmode** -- a string or "None"

   Set the resizemode to "auto", "user" or "noresize". If *rmode* is
   not given, return the current resizemode. The different resizemodes
   have the following effects:

   * "auto": the turtle is resized according to the value of
     "pensize()".

   * "user": the turtle is resized according to the stretch factors
     and outline width, which are set by "shapesize()".

   * "noresize": the turtle is not resized.

   "resizemode("user")" is called by "shapesize()" when used with
   arguments.

      >>> turtle.resizemode()
      'noresize'
      >>> turtle.resizemode("auto")
      >>> turtle.resizemode()
      'auto'

turtle.shapesize(stretch_wid=None, stretch_len=None, outline=None)
turtle.turtlesize(stretch_wid=None, stretch_len=None, outline=None)

   Parameters:
      * **stretch_wid** -- a positive number or "None"

      * **stretch_len** -- a positive number or "None"

      * **outline** -- a positive number or "None"

   Return or set the turtle's stretch factors and outline width. If no
   arguments are given, return the current values. Otherwise set
   resizemode to "user", so that the turtle is displayed stretched
   according to its stretch factors:

   * *stretch_wid*: the stretch factor perpendicular to the turtle's
     heading

   * *stretch_len*: the stretch factor in the direction of the
     turtle's heading

   * *outline*: the width of the shape's outline

   For example, "shapesize(2, 1)" makes the turtle twice as wide
   without changing its length. If only *stretch_wid* is given,
   *stretch_len* is set to the same value.

      >>> turtle.shapesize()
      (1.0, 1.0, 1)
      >>> turtle.resizemode("user")
      >>> turtle.shapesize(5, 5, 12)
      >>> turtle.shapesize()
      (5, 5, 12)
      >>> turtle.shapesize(outline=8)
      >>> turtle.shapesize()
      (5, 5, 8)

turtle.shearfactor(shear=None)

   Parameters:
      **shear** -- a number or "None"

   Return or set the current shear factor. Shearing slants the turtle
   shape, like the slant of italic letters. The shear factor says how
   much it is slanted: 0 is not slanted at all, and the larger the
   number, the stronger the slant. Negative numbers slant the other
   way. If *shear* is not given, return the current shear factor.
   Otherwise slant the turtle shape accordingly and set resizemode to
   "user". The turtle's heading does not change. Precisely, the shear
   factor is the tangent of the shear angle.

      >>> turtle.shape("circle")
      >>> turtle.shapesize(5,2)
      >>> turtle.shearfactor(0.5)
      >>> turtle.shearfactor()
      0.5

turtle.tilt(angle)

   Parameters:
      **angle** -- a number

   Turn the turtle shape by *angle* from its current tilt angle. The
   turtle's heading does not change, so the turtle keeps moving in the
   same direction. See "tiltangle()".

      >>> turtle.reset()
      >>> turtle.shape("circle")
      >>> turtle.shapesize(5,2)
      >>> turtle.tilt(30)
      >>> turtle.fd(50)
      >>> turtle.tilt(30)
      >>> turtle.fd(50)

turtle.tiltangle(angle=None)

   Parameters:
      **angle** -- a number or "None"

   Return or set the current tilt angle. The tilt angle is the angle
   between the direction the turtle shape points in and the direction
   the turtle moves in. Normally the shape points in the direction of
   movement, so the tilt angle is 0. If *angle* is given, turn the
   turtle shape to that tilt angle, no matter what it was before, and
   set resizemode to "user". The turtle's heading does not change. If
   *angle* is not given, return the current tilt angle.

      >>> turtle.reset()
      >>> turtle.shape("circle")
      >>> turtle.shapesize(5,2)
      >>> turtle.tilt(45)
      >>> turtle.tiltangle()
      45.0

turtle.shapetransform(t11=None, t12=None, t21=None, t22=None)

   Parameters:
      * **t11** -- a number or "None"

      * **t12** -- a number or "None"

      * **t21** -- a number or "None"

      * **t22** -- a number or "None"

   Return or set the transformation matrix of the turtle shape. The
   matrix combines the stretch factors, the shear factor and the tilt
   angle of the turtle shape into four numbers: *t11* and *t12* form
   its first row, *t21* and *t22* its second. If none of them are
   given, return the current matrix as a tuple of four numbers.
   Otherwise set the given elements and update the stretch factors,
   shear factor and tilt angle accordingly. "t11 * t22 - t12 * t21"
   must not be zero, otherwise an error is raised.

      >>> turtle = Turtle()
      >>> turtle.shape("square")
      >>> turtle.shapesize(4,2)
      >>> turtle.shearfactor(-0.5)
      >>> turtle.shapetransform()
      (4.0, -1.0, -0.0, 2.0)

turtle.get_shapepoly()

   Return the points that form the outline of the current turtle shape
   as a tuple of "(x, y)" coordinate pairs. These points can be used
   to define a new shape or parts of a compound shape

      >>> turtle.shape("square")
      >>> turtle.shapetransform(4, -1, 0, 2)
      >>> turtle.get_shapepoly()
      ((50, -20), (30, 20), (-50, 20), (-30, -20))


Using events
~~~~~~~~~~~~

turtle.onclick(fun, btn=1, add=None)

   Parameters:
      * **fun** -- a function with two arguments or "None"

      * **btn** -- an integer

      * **add** -- a boolean or "None"

   Bind *fun* to mouse-click events on this turtle. *fun* is called
   with the coordinates of the clicked point on the canvas. If *fun*
   is "None", existing bindings are removed. *btn* is the number of
   the mouse button and defaults to 1, the left mouse button. If *add*
   is "True", a new binding is added, otherwise it replaces a former
   binding. Example for the anonymous turtle, that is, the procedural
   way:

      >>> def turn(x, y):
      ...     left(180)
      ...
      >>> onclick(turn)  # Now clicking into the turtle will turn it.
      >>> onclick(None)  # event-binding will be removed

turtle.onrelease(fun, btn=1, add=None)

   Parameters:
      * **fun** -- a function with two arguments which will be called
        with the coordinates of the clicked point on the canvas

      * **btn** -- number of the mouse-button, defaults to 1 (left
        mouse button)

      * **add** -- "True" or "False" -- if "True", a new binding will
        be added, otherwise it will replace a former binding

   Bind *fun* to mouse-button-release events on this turtle.  If *fun*
   is "None", existing bindings are removed.

      >>> class MyTurtle(Turtle):
      ...     def glow(self,x,y):
      ...         self.fillcolor("red")
      ...     def unglow(self,x,y):
      ...         self.fillcolor("")
      ...
      >>> turtle = MyTurtle()
      >>> turtle.onclick(turtle.glow)     # clicking on turtle turns fillcolor red,
      >>> turtle.onrelease(turtle.unglow) # releasing turns it to transparent.

turtle.ondrag(fun, btn=1, add=None)

   Parameters:
      * **fun** -- a function with two arguments which will be called
        with the coordinates of the clicked point on the canvas

      * **btn** -- number of the mouse-button, defaults to 1 (left
        mouse button)

      * **add** -- "True" or "False" -- if "True", a new binding will
        be added, otherwise it will replace a former binding

   Bind *fun* to mouse-move events on this turtle.  If *fun* is
   "None", existing bindings are removed.

   Remark: Every sequence of mouse-move-events on a turtle is preceded
   by a mouse-click event on that turtle.

      >>> turtle.ondrag(turtle.goto)

   Subsequently, clicking and dragging the Turtle will move it across
   the screen thereby producing handdrawings (if pen is down).


Special Turtle methods
~~~~~~~~~~~~~~~~~~~~~~

turtle.poly()

   Record the vertices of a polygon drawn in the "with" block. The
   first and last vertices will be connected.

      >>> with turtle.poly():
      ...     turtle.forward(100)
      ...     turtle.right(60)
      ...     turtle.forward(100)

   "poly()" is a *context manager*, so using it is the same as calling
   "begin_poly()" before the block and "end_poly()" after it:

      >>> turtle.begin_poly()
      >>> turtle.forward(100)
      >>> turtle.right(60)
      >>> turtle.forward(100)
      >>> turtle.end_poly()

   Added in version 3.14.

turtle.begin_poly()

   Start recording the vertices of a polygon. The current turtle
   position is the first vertex of the polygon.

turtle.end_poly()

   Stop recording the vertices of a polygon. The current turtle
   position is the last vertex of the polygon. This will be connected
   with the first vertex.

turtle.get_poly()

   Return the last recorded polygon.

      >>> turtle.home()
      >>> turtle.begin_poly()
      >>> turtle.fd(100)
      >>> turtle.left(20)
      >>> turtle.fd(30)
      >>> turtle.left(60)
      >>> turtle.fd(50)
      >>> turtle.end_poly()
      >>> p = turtle.get_poly()
      >>> register_shape("myFavouriteShape", p)

turtle.clone()

   Create and return a clone of the turtle. The clone has the same
   position, heading and turtle properties.

      >>> leonel = Turtle()
      >>> marco = leonel.clone()

turtle.getturtle()
turtle.getpen()

   Return the Turtle object itself.

   Call "getturtle()" to get the turtle used by functions such as
   "forward()" and "left()":

      >>> pet = getturtle()
      >>> pet.fd(50)
      >>> pet
      <turtle.Turtle object at 0x...>

turtle.getscreen()

   Return the "TurtleScreen" object the turtle is drawing on.
   TurtleScreen methods can then be called for that object.

      >>> ts = turtle.getscreen()
      >>> ts
      <turtle._Screen object at 0x...>
      >>> ts.bgcolor("pink")

turtle.setundobuffer(size)

   Parameters:
      **size** -- an integer or "None"

   Set or disable the undo buffer. If *size* is an integer, an empty
   undo buffer of the given size is installed. *size* is the maximum
   number of turtle actions that can be undone by "undo()". If *size*
   is "None", the undo buffer is disabled.

      >>> turtle.setundobuffer(42)

turtle.undobufferentries()

   Return the number of entries in the undo buffer.

      >>> while undobufferentries():
      ...     undo()


Screen methods and functions
----------------------------

Most of the examples in this section refer to a TurtleScreen instance
called "screen".


Window control
~~~~~~~~~~~~~~

turtle.bgcolor()
turtle.bgcolor(color, /)
turtle.bgcolor(r, g, b, /)

   Return or set the background color of the TurtleScreen.

   Four input formats are allowed:

   "bgcolor()"
      Return the current background color as a color specification
      string or as a tuple (see example).  May be used as input to
      another "color()", "pencolor()", "fillcolor()" or "bgcolor()"
      call.

   "bgcolor(colorstring)"
      Set the background color to *colorstring*, which is a Tk color
      specification string, such as ""red"", ""yellow"", or
      ""#33cc8c"".

   "bgcolor((r, g, b))"
      Set the background color to the RGB color represented by the
      tuple of *r*, *g*, and *b*. Each of *r*, *g*, and *b* must be
      between 0 and colormode, where colormode is either 1.0 or 255
      (see "colormode()").

   "bgcolor(r, g, b)"
      Set the background color to the RGB color represented by *r*,
      *g*, and *b*. Each of *r*, *g*, and *b* must be between 0 and
      colormode.

      >>> screen.bgcolor("orange")
      >>> screen.bgcolor()
      'orange'
      >>> screen.bgcolor("#800080")
      >>> screen.bgcolor()
      (128.0, 0.0, 128.0)

turtle.bgpic(picname=None)

   Parameters:
      **picname** -- a string or "None"

   Set the background image or return the name of the current one. If
   *picname* is the name of an image file (PNG, GIF, PGM, and PPM),
   set that image as the background. If *picname* is ""nopic"", delete
   the background image, if present. If *picname* is "None", return
   the filename of the current background image.

      >>> screen.bgpic()
      'nopic'
      >>> screen.bgpic("landscape.gif")
      >>> screen.bgpic()
      'landscape.gif'

turtle.clear()

   Note:

     This TurtleScreen method is available as a global function only
     under the name "clearscreen".  The global function "clear" is a
     different one derived from the Turtle method "clear".

turtle.clearscreen()

   Delete all drawings and all turtles from the TurtleScreen.  Reset
   the now empty TurtleScreen to its initial state: white background,
   no background image, no event bindings and tracing on.

turtle.reset()

   Note:

     This TurtleScreen method is available as a global function only
     under the name "resetscreen".  The global function "reset" is
     another one derived from the Turtle method "reset".

turtle.resetscreen()

   Reset all turtles on the screen to their initial state.

turtle.screensize(canvwidth=None, canvheight=None, bg=None)

   Parameters:
      * **canvwidth** -- a positive integer or "None"

      * **canvheight** -- a positive integer or "None"

      * **bg** -- a colorstring or a color tuple or "None"

   Resize the canvas the turtles are drawing on. *canvwidth* and
   *canvheight* are the new width and height of the canvas in pixels,
   and *bg* is the new background color. If no arguments are given,
   return the current canvas width and height.

   The drawing window is not altered. To see hidden parts of the
   canvas, use the scrollbars. This can make visible those parts of a
   drawing which were outside the canvas before, for example to find a
   turtle that has wandered off the canvas.

      >>> screen.screensize()
      (400, 300)
      >>> screen.screensize(2000,1500)
      >>> screen.screensize()
      (2000, 1500)

turtle.setworldcoordinates(llx, lly, urx, ury)

   Parameters:
      * **llx** -- a number

      * **lly** -- a number

      * **urx** -- a number

      * **ury** -- a number

   Set up a user-defined coordinate system. *llx* and *lly* are the x
   and y coordinates of the lower left corner of the canvas. *urx* and
   *ury* are the x and y coordinates of the upper right corner. Switch
   to mode "world" if necessary, which performs a reset. If mode
   "world" is already active, all drawings are redrawn according to
   the new coordinates. In user-defined coordinate systems, angles may
   appear distorted, see "mode()".

      >>> screen.reset()
      >>> screen.setworldcoordinates(-50,-7.5,50,7.5)
      >>> for _ in range(72):
      ...     left(10)
      ...
      >>> for _ in range(8):
      ...     left(45); fd(2)   # a regular octagon


Animation control
~~~~~~~~~~~~~~~~~

turtle.no_animation()

   Temporarily turn off turtle animation. The code inside the "with"
   block is not animated. Once the block is exited, the drawing
   appears. This is useful for drawing complex shapes where even the
   fastest speed setting is too slow.

      >>> with screen.no_animation():
      ...     for dist in range(2, 400, 2):
      ...         fd(dist)
      ...         rt(90)

   Added in version 3.14.

turtle.delay(delay=None)

   Parameters:
      **delay** -- a nonnegative integer or "None"

   Return or set the drawing delay in milliseconds. This is
   approximately the time interval between two consecutive canvas
   updates. The longer the drawing delay, the slower the animation.

      >>> screen.delay()
      10
      >>> screen.delay(5)
      >>> screen.delay()
      5

turtle.tracer(n=None, delay=None)

   Parameters:
      * **n** -- a nonnegative integer or "None"

      * **delay** -- a nonnegative integer or "None"

   Turn turtle animation on or off and set the drawing delay. If *n*
   is given, only every n-th regular screen update is performed, which
   can be used to speed up the drawing of complex graphics. If *n* is
   0, animation is turned off and the screen is only updated by
   calling "update()". If *delay* is given, it sets the drawing delay,
   see "delay()". When called without arguments, return the current
   value of *n*.

      >>> screen.tracer(8, 25)
      >>> dist = 2
      >>> for i in range(200):
      ...     fd(dist)
      ...     rt(90)
      ...     dist += 2

turtle.update()

   Perform a TurtleScreen update. To be used when tracer is turned
   off.

See also the RawTurtle/Turtle method "speed()".


Using screen events
~~~~~~~~~~~~~~~~~~~

turtle.listen(xdummy=None, ydummy=None)

   Parameters:
      * **xdummy** -- ignored

      * **ydummy** -- ignored

   Set focus on the "TurtleScreen" so that it receives key events. The
   two dummy arguments are only there so that "listen()" can be passed
   to "onclick()".

turtle.onkey(fun, key)
turtle.onkeyrelease(fun, key)

   Parameters:
      * **fun** -- a function with no arguments or "None"

      * **key** -- a string

   Bind *fun* to the key-release event of *key*. *key* is a key, such
   as "a", or a key symbol, such as "space". If *fun* is "None", the
   event binding is removed. To be able to receive key events, the
   "TurtleScreen" must have focus, see "listen()".

      >>> def f():
      ...     fd(50)
      ...     lt(60)
      ...
      >>> screen.onkey(f, "Up")
      >>> screen.listen()

   The turtle can then be moved by repeatedly pressing the up-arrow
   key, drawing a hexagon.

turtle.onkeypress(fun, key=None)

   Parameters:
      * **fun** -- a function with no arguments or "None"

      * **key** -- a string or "None"

   Bind *fun* to the key-press event of *key*. *key* is a key, such as
   "a", or a key symbol, such as "space". If *key* is not given, *fun*
   is bound to the key-press event of any key. If *fun* is "None", the
   event binding is removed. To be able to receive key events, the
   "TurtleScreen" must have focus, see "listen()".

      >>> def f():
      ...     fd(50)
      ...     lt(60)
      ...
      >>> screen.onkeypress(f, "Up")
      >>> screen.listen()

   The turtle can then be moved by pressing or holding down the up-
   arrow key, drawing a hexagon.

turtle.onclick(fun, btn=1, add=None)
turtle.onscreenclick(fun, btn=1, add=None)

   Parameters:
      * **fun** -- a function with two arguments or "None"

      * **btn** -- an integer

      * **add** -- a boolean or "None"

   Bind *fun* to mouse-click events on this screen. *fun* is called
   with the coordinates of the clicked point on the canvas. If *fun*
   is "None", existing bindings are removed. *btn* is the number of
   the mouse button and defaults to 1, the left mouse button. If *add*
   is "True", a new binding is added, otherwise it replaces a former
   binding.

   Example for a TurtleScreen instance named "screen" and a Turtle
   instance named "turtle":

      >>> screen.onclick(turtle.goto) # Subsequently clicking into the TurtleScreen will
      >>>                             # make the turtle move to the clicked point.
      >>> screen.onclick(None)        # remove event binding again

   Note:

     This TurtleScreen method is available as a global function only
     under the name "onscreenclick".  The global function "onclick" is
     another one derived from the Turtle method "onclick".

turtle.ontimer(fun, t=0)

   Parameters:
      * **fun** -- a function with no arguments

      * **t** -- a nonnegative number

   Install a timer that calls *fun* after *t* milliseconds.

      >>> running = True
      >>> def f():
      ...     if running:
      ...         fd(50)
      ...         lt(60)
      ...         screen.ontimer(f, 250)
      >>> f()  # makes the turtle march around
      >>> running = False

turtle.mainloop()
turtle.done()

   Start the event loop by calling Tkinter's "mainloop()" method. Must
   be the last statement in a turtle graphics program. Must *not* be
   used if a script is run from within IDLE in -n mode (see Running
   without a subprocess).


Input methods
~~~~~~~~~~~~~

turtle.textinput(title, prompt)

   Parameters:
      * **title** -- a string

      * **prompt** -- a string

   Pop up a dialog window for input of a string. *title* is the title
   of the dialog window and *prompt* is a text describing what
   information to input. Return the string entered. If the dialog is
   canceled, return "None".

      >>> screen.textinput("NIM", "Name of first player:")

turtle.numinput(title, prompt, default=None, minval=None, maxval=None)

   Parameters:
      * **title** -- a string

      * **prompt** -- a string

      * **default** -- a number or "None"

      * **minval** -- a number or "None"

      * **maxval** -- a number or "None"

   Pop up a dialog window for input of a number. *title* is the title
   of the dialog window and *prompt* is a text describing what
   numerical information to input. *default* is the default value,
   *minval* and *maxval* are the minimum and maximum values for input.
   If these are given, the number entered must be between *minval* and
   *maxval*. If not, a hint is issued and the dialog remains open for
   correction. Return the number entered. If the dialog is canceled,
   return "None".

      >>> screen.numinput("Poker", "Your stakes:", 1000, minval=10, maxval=10000)


Settings and special methods
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

turtle.mode(mode=None)

   Parameters:
      **mode** -- a string or "None"

   Set the turtle mode and perform a reset. *mode* is one of the
   strings "standard", "logo" or "world". If *mode* is not given,
   return the current mode.

   Mode "standard" is compatible with the old "turtle" module. Mode
   "logo" is compatible with most Logo turtle graphics. Mode "world"
   uses user-defined world coordinates, see "setworldcoordinates()".
   In this mode, angles appear distorted if the x and y units are not
   of equal length.

   +--------------+---------------------------+---------------------+
   | Mode         | Initial turtle heading    | positive angles     |
   |==============|===========================|=====================|
   | "standard"   | to the right (east)       | counterclockwise    |
   +--------------+---------------------------+---------------------+
   | "logo"       | upward    (north)         | clockwise           |
   +--------------+---------------------------+---------------------+

      >>> mode("logo")  # resets turtle heading to north
      >>> mode()
      'logo'

turtle.colormode(cmode=None)

   Parameters:
      **cmode** -- a number or "None"

   Return the colormode or set it to 1.0 or 255. After setting it, the
   *r*, *g* and *b* values of color triples have to be between 0 and
   *cmode*.

      >>> screen.colormode(1)
      >>> turtle.pencolor(240, 160, 80)
      Traceback (most recent call last):
           ...
      TurtleGraphicsError: bad color sequence: (240, 160, 80)
      >>> screen.colormode()
      1.0
      >>> screen.colormode(255)
      >>> screen.colormode()
      255
      >>> turtle.pencolor(240,160,80)

turtle.getcanvas()

   Return the Canvas of this TurtleScreen.  Useful for insiders who
   know what to do with a Tkinter Canvas.

      >>> cv = screen.getcanvas()
      >>> cv
      <turtle.ScrolledCanvas object ...>

turtle.getshapes()

   Return a list of names of all currently available turtle shapes.

      >>> screen.getshapes()
      ['arrow', 'blank', 'circle', ..., 'turtle']

turtle.register_shape(name, shape=None)
turtle.addshape(name, shape=None)

   Parameters:
      * **name** -- a string

      * **shape** -- a string, a tuple of pairs of numbers, a "Shape"
        object or "None"

   Add a turtle shape to the TurtleScreen's shape list. It can be
   called in four different ways:

   1. *name* is the name of an image file (PNG, GIF, PGM, and PPM) and
      *shape* is "None": Install the corresponding image shape.

         >>> screen.register_shape("turtle.gif")

   2. *name* is an arbitrary string and *shape* is the name of an
      image file (PNG, GIF, PGM, and PPM): Install the corresponding
      image shape.

         >>> screen.register_shape("turtle", "turtle.gif")

   3. *name* is an arbitrary string and *shape* is a tuple of pairs of
      coordinates: Install the corresponding polygon shape.

         >>> screen.register_shape("triangle", ((5,-3), (0,5), (-5,-3)))

   4. *name* is an arbitrary string and *shape* is a (compound)
      "Shape" object: Install the corresponding compound shape.

   Image shapes do not rotate when turning the turtle, so they do not
   display the heading of the turtle. To use a registered shape, call
   "shape()" with its name.

   Changed in version 3.14: Added support for PNG, PGM, and PPM image
   formats. Both a shape name and an image file name can be specified.

turtle.turtles()

   Return the list of turtles on the screen.

      >>> for turtle in screen.turtles():
      ...     turtle.color("red")

turtle.window_height()

   Return the height of the turtle window.

      >>> screen.window_height()
      480

turtle.window_width()

   Return the width of the turtle window.

      >>> screen.window_width()
      640


Screen-only methods
~~~~~~~~~~~~~~~~~~~

turtle.bye()

   Close the turtle graphics window.

turtle.exitonclick()

   Bind "bye()" method to mouse clicks on the Screen.

   If the value "using_IDLE" in the configuration dictionary is
   "False" (default value), also enter mainloop.  Remark: If IDLE with
   the "-n" switch (no subprocess) is used, this value should be set
   to "True" in "turtle.cfg".  In this case IDLE's own mainloop is
   active also for the client script.

turtle.save(filename, *, overwrite=False)

   Parameters:
      * **filename** -- a string

      * **overwrite** -- a boolean

   Save the current drawing and the turtles as a PostScript file.
   *filename* is the path of the file to create. It must end with
   "".ps"" or "".eps"". If a file with that name already exists, a
   "FileExistsError" is raised, unless *overwrite* is "True".
   *overwrite* must be given by name, as in "overwrite=True".

      >>> screen.save("my_drawing.ps")
      >>> screen.save("my_drawing.ps", overwrite=True)

   Added in version 3.14.

turtle.setup(width=_CFG['width'], height=_CFG['height'], startx=_CFG['leftright'], starty=_CFG['topbottom'])

   Set the size and position of the main window.  Default values of
   arguments are stored in the configuration dictionary and can be
   changed via a "turtle.cfg" file.

   Parameters:
      * **width** -- if an integer, a size in pixels, if a float, a
        fraction of the screen; default is 50% of screen

      * **height** -- if an integer, the height in pixels, if a float,
        a fraction of the screen; default is 75% of screen

      * **startx** -- if positive, starting position in pixels from
        the left edge of the screen, if negative from the right edge,
        if "None", center window horizontally

      * **starty** -- if positive, starting position in pixels from
        the top edge of the screen, if negative from the bottom edge,
        if "None", center window vertically

      >>> screen.setup (width=200, height=200, startx=0, starty=0)
      >>>              # sets window to 200x200 pixels, in upper left of screen
      >>> screen.setup(width=.75, height=0.5, startx=None, starty=None)
      >>>              # sets window to 75% of screen by 50% of screen and centers

turtle.title(titlestring)

   Parameters:
      **titlestring** -- a string

   Set the title of the turtle window to *titlestring*. The title is
   shown in the title bar of the turtle graphics window.

      >>> screen.title("Welcome to the turtle zoo!")


Public classes
--------------

class turtle.RawTurtle(canvas)
class turtle.RawPen(canvas)

   Parameters:
      **canvas** -- a "tkinter.Canvas", a "ScrolledCanvas" or a
      "TurtleScreen"

   Create a turtle.  The turtle has all methods described above as
   "methods of Turtle/RawTurtle".

class turtle.Turtle

   Subclass of RawTurtle, has the same interface but draws on a
   default "Screen" object created automatically when needed for the
   first time.

class turtle.TurtleScreen(cv)

   Parameters:
      **cv** -- a "tkinter.Canvas"

   Provides screen oriented methods like "bgcolor()" etc. that are
   described above.

class turtle.Screen

   Subclass of "TurtleScreen", with four methods added. Calling
   "Screen()" returns the single screen object. If it does not exist
   yet, it is created. Otherwise the existing one is returned.

class turtle.ScrolledCanvas(master)

   Parameters:
      **master** -- some Tkinter widget to contain the ScrolledCanvas,
      i.e. a Tkinter-canvas with scrollbars added

   Used by class Screen, which thus automatically provides a
   ScrolledCanvas as playground for the turtles.

class turtle.Shape(type_, data)

   Parameters:
      * **type_** -- a string

      * **data** -- depends on *type_*

   Data structure modeling shapes. *type_* is one of the strings
   "polygon", "image" or "compound". What *data* must be depends on
   *type_*: for "polygon" a tuple of pairs of coordinates, for "image"
   an image (only used internally), and for "compound" "None", as a
   compound shape is built up using the "addcomponent()" method.

   addcomponent(poly, fill, outline=None)

      Parameters:
         * **poly** -- a tuple of pairs of numbers

         * **fill** -- a color

         * **outline** -- a color or "None"

      Add a component to a shape of type "compound". *poly* is a
      polygon, a tuple of pairs of numbers. *fill* is the color the
      polygon is filled with and *outline* is the color of its
      outline. If *outline* is not given, *fill* is used for it as
      well.

      Example:

         >>> poly = ((0,0), (10,-5), (0,10), (-10,-5))
         >>> s = Shape("compound")
         >>> s.addcomponent(poly, "red", "blue")
         >>> # ... add more components and then use register_shape()

      See How to use compound shapes.

class turtle.Vec2D(x, y)

   A two-dimensional vector class, used as a helper class for
   implementing turtle graphics.  May be useful for turtle graphics
   programs too.  Derived from tuple, so a vector is a tuple!

   Provides (for *a*, *b* vectors, *k* number):

   * "a + b" vector addition

   * "a - b" vector subtraction

   * "a * b" inner product

   * "k * a" and "a * k" multiplication with scalar

   * "abs(a)" absolute value of a

   * "a.rotate(angle)" rotation


Exceptions
----------

The "turtle" module defines the following exception:

exception turtle.TurtleGraphicsError

   Raised for invalid arguments or operations. For example, a
   malformed color string:

      >>> turtle.color("blau")
      Traceback (most recent call last):
          ...
      turtle.TurtleGraphicsError: bad color string: blau


How-to guides
=============

This section covers some typical turtle use-cases and approaches.


How to automatically begin and end filling
------------------------------------------

Starting with Python 3.14, you can use the "fill()" *context manager*
instead of "begin_fill()" and "end_fill()" to automatically begin and
end fill. Here is an example:

   with fill():
       for i in range(4):
           forward(100)
           right(90)

   forward(200)

The code above is equivalent to:

   begin_fill()
   for i in range(4):
       forward(100)
       right(90)
   end_fill()

   forward(200)


How to use compound shapes
--------------------------

To use compound turtle shapes, which consist of several polygons of
different color, you must use the helper class "Shape" explicitly as
described below:

1. Create an empty "Shape" object of type "compound".

2. Add as many components to this object as desired, using the
   "addcomponent()" method.

   For example:

      >>> s = Shape("compound")
      >>> poly1 = ((0,0), (10,-5), (0,10), (-10,-5))
      >>> s.addcomponent(poly1, "red", "blue")
      >>> poly2 = ((0,0), (10,-5), (-10,-5))
      >>> s.addcomponent(poly2, "blue", "red")

3. Now add the Shape to the Screen's shapelist and use it:

      >>> register_shape("myshape", s)
      >>> shape("myshape")


How to use the "turtle" module namespace
----------------------------------------

Using "from turtle import *" is convenient - but be warned that it
imports a rather large collection of objects, and if you're doing
anything but turtle graphics you run the risk of a name conflict (this
becomes even more an issue if you're using turtle graphics in a script
where other modules might be imported).

The solution is to use "import turtle" - "fd()" becomes "turtle.fd()",
"width()" becomes "turtle.width()" and so on. (If typing "turtle" over
and over again becomes tedious, use for example "import turtle as t"
instead.)


How to use turtle graphics in a script
--------------------------------------

It's recommended to use the "turtle" module namespace as described
immediately above, for example:

   import turtle as t
   from random import random

   for i in range(100):
       steps = int(random() * 100)
       angle = int(random() * 360)
       t.right(angle)
       t.fd(steps)

Another step is also required though - as soon as the script ends,
Python will also close the turtle's window. Add:

   t.mainloop()

to the end of the script. The script will now wait to be dismissed and
will not exit until it is terminated, for example by closing the
turtle graphics window.


How to use object-oriented turtle graphics
------------------------------------------

See also: Explanation of the object-oriented interface

Other than for very basic introductory purposes, or for trying things
out as quickly as possible, it's more usual and much more powerful to
use the object-oriented approach to turtle graphics. For example, this
allows multiple turtles on screen at once.

In this approach, the various turtle commands are methods of objects
(mostly of "Turtle" objects). You *can* use the object-oriented
approach in the shell, but it would be more typical in a Python
script.

The example above then becomes:

   from turtle import Turtle
   from random import random

   t = Turtle()
   for i in range(100):
       steps = int(random() * 100)
       angle = int(random() * 360)
       t.right(angle)
       t.fd(steps)

   t.screen.mainloop()

Note the last line. "t.screen" is an instance of the "Screen" that a
Turtle instance exists on; it's created automatically along with the
turtle.

The turtle's screen can be customised, for example:

   t.screen.title('Object-oriented turtle demo')
   t.screen.bgcolor("orange")


How to use "help()"
-------------------

The public methods of the Screen and Turtle classes are documented
extensively via docstrings.  So these can be used as online-help via
the Python help facilities:

* When using IDLE, tooltips show the signatures and first lines of the
  docstrings of typed in function-/method calls.

* Calling "help()" on methods or functions displays the docstrings:

     >>> help(Screen.bgcolor)
     Help on method bgcolor in module turtle:

     bgcolor(self, *args) unbound turtle.Screen method
         Set or return backgroundcolor of the TurtleScreen.

         Arguments (if given): a color string or three numbers
         in the range 0..colormode or a 3-tuple of such numbers.


         >>> screen.bgcolor("orange")
         >>> screen.bgcolor()
         "orange"
         >>> screen.bgcolor(0.5,0,0.5)
         >>> screen.bgcolor()
         "#800080"

     >>> help(Turtle.penup)
     Help on method penup in module turtle:

     penup(self) unbound turtle.Turtle method
         Pull the pen up -- no drawing when moving.

         Aliases: penup | pu | up

         No argument

         >>> turtle.penup()

* The docstrings of the functions which are derived from methods have
  a modified form:

     >>> help(bgcolor)
     Help on function bgcolor in module turtle:

     bgcolor(*args)
         Set or return backgroundcolor of the TurtleScreen.

         Arguments (if given): a color string or three numbers
         in the range 0..colormode or a 3-tuple of such numbers.

         Example::

           >>> bgcolor("orange")
           >>> bgcolor()
           "orange"
           >>> bgcolor(0.5,0,0.5)
           >>> bgcolor()
           "#800080"

     >>> help(penup)
     Help on function penup in module turtle:

     penup()
         Pull the pen up -- no drawing when moving.

         Aliases: penup | pu | up

         No argument

         Example:
         >>> penup()

These modified docstrings are created automatically together with the
function definitions that are derived from the methods at import time.


Translation of docstrings into different languages
--------------------------------------------------

There is a utility to create a dictionary the keys of which are the
method names and the values of which are the docstrings of the public
methods of the classes Screen and Turtle.

turtle.write_docstringdict(filename='turtle_docstringdict')

   Parameters:
      **filename** -- a string, used as filename

   Create and write docstring-dictionary to a Python script with the
   given filename.  This function has to be called explicitly (it is
   not used by the turtle graphics classes).  The docstring dictionary
   will be written to the Python script "*filename*.py".  It is
   intended to serve as a template for translation of the docstrings
   into different languages.

If you (or your students) want to use "turtle" with online help in
your native language, you have to translate the docstrings and save
the resulting file as e.g. "turtle_docstringdict_german.py".

If you have an appropriate entry in your "turtle.cfg" file this
dictionary will be read in at import time and will replace the
original English docstrings.

At the time of this writing there are docstring dictionaries in German
and in Italian.  (Requests please to glingl@aon.at.)


How to configure Screen and Turtles
-----------------------------------

The built-in default configuration mimics the appearance and behaviour
of the old turtle module in order to retain best possible
compatibility with it.

If you want to use a different configuration which better reflects the
features of this module or which better fits to your needs, e.g. for
use in a classroom, you can prepare a configuration file "turtle.cfg"
which will be read at import time and modify the configuration
according to its settings.

The built in configuration would correspond to the following
"turtle.cfg":

   width = 0.5
   height = 0.75
   leftright = None
   topbottom = None
   canvwidth = 400
   canvheight = 300
   mode = standard
   colormode = 1.0
   delay = 10
   undobuffersize = 1000
   shape = classic
   pencolor = black
   fillcolor = black
   resizemode = noresize
   visible = True
   language = english
   exampleturtle = turtle
   examplescreen = screen
   title = Python Turtle Graphics
   using_IDLE = False

Short explanation of selected entries:

* The first four lines correspond to the arguments of the
  "Screen.setup" method.

* Line 5 and 6 correspond to the arguments of the method
  "Screen.screensize".

* *shape* can be any of the built-in shapes, e.g: arrow, turtle, etc.
  For more info try "help(shape)".

* If you want to use no fill color (i.e. make the turtle transparent),
  you have to write "fillcolor = """ (but all nonempty strings must
  not have quotes in the cfg file).

* If you want to reflect the turtle its state, you have to use
  "resizemode = auto".

* If you set e.g. "language = italian" the docstringdict
  "turtle_docstringdict_italian.py" will be loaded at import time (if
  present on the import path, e.g. in the same directory as "turtle").

* The entries *exampleturtle* and *examplescreen* define the names of
  these objects as they occur in the docstrings.  The transformation
  of method-docstrings to function-docstrings will delete these names
  from the docstrings.

* *using_IDLE*: Set this to "True" if you regularly work with IDLE and
  its "-n" switch ("no subprocess").  This will prevent
  "exitonclick()" to enter the mainloop.

There can be a "turtle.cfg" file in the directory where "turtle" is
stored and an additional one in the current working directory.  The
latter will override the settings of the first one.

The "Lib/turtledemo" directory contains a "turtle.cfg" file.  You can
study it as an example and see its effects when running the demos
(preferably not from within the demo-viewer).


Explanation
===========

A turtle object draws on a screen object, and there a number of key
classes in the turtle object-oriented interface that can be used to
create them and relate them to each other.

A "Turtle" instance will automatically create a "Screen" instance if
one is not already present.

"Turtle" is a subclass of "RawTurtle", which *doesn't* automatically
create a drawing surface - a *canvas* will need to be provided or
created for it. The *canvas* can be a "tkinter.Canvas",
"ScrolledCanvas" or "TurtleScreen".

"TurtleScreen" is the basic drawing surface for a turtle. "Screen" is
a subclass of "TurtleScreen", and includes some additional methods for
managing its appearance (including size and title) and behaviour.
"TurtleScreen"'s constructor needs a "tkinter.Canvas" or a
"ScrolledCanvas" as an argument.

The functional interface for turtle graphics uses the various methods
of "Turtle" and "TurtleScreen"/"Screen". Behind the scenes, a screen
object is automatically created whenever a function derived from a
"Screen" method is called. Similarly, a turtle object is automatically
created whenever any of the functions derived from a Turtle method is
called.

To use multiple turtles on a screen, the object-oriented interface
must be used.


"turtledemo" --- Demo scripts
=============================

The "turtledemo" package includes a set of demo scripts.  These
scripts can be run and viewed using the supplied demo viewer as
follows:

   python -m turtledemo

Alternatively, you can run the demo scripts individually.  For
example,

   python -m turtledemo.bytedesign

The "turtledemo" package directory contains:

* A demo viewer "__main__.py" which can be used to view the sourcecode
  of the scripts and run them at the same time.

* Multiple scripts demonstrating different features of the "turtle"
  module.  Examples can be accessed via the Examples menu.  They can
  also be run standalone.

* A "turtle.cfg" file which serves as an example of how to write and
  use such files.

The demo scripts are:

+--------------------------+--------------------------------+----------------------------------------+
| Name                     | Description                    | Features                               |
|==========================|================================|========================================|
| "bytedesign"             | complex classical turtle       | "tracer()", "delay()", "update()"      |
|                          | graphics pattern               |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "chaos"                  | graphs Verhulst dynamics,      | world coordinates                      |
|                          | shows that computer's          |                                        |
|                          | computations can generate      |                                        |
|                          | results sometimes against the  |                                        |
|                          | common sense expectations      |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "clock"                  | analog clock showing time of   | turtles as clock's hands, "ontimer()"  |
|                          | your computer                  |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "colormixer"             | experiment with r, g, b        | "ondrag()"                             |
+--------------------------+--------------------------------+----------------------------------------+
| "forest"                 | 3 breadth-first trees          | randomization                          |
+--------------------------+--------------------------------+----------------------------------------+
| "fractalcurves"          | Hilbert & Koch curves          | recursion                              |
+--------------------------+--------------------------------+----------------------------------------+
| "lindenmayer"            | ethnomathematics (indian       | L-System                               |
|                          | kolams)                        |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "minimal_hanoi"          | Towers of Hanoi                | Rectangular Turtles as Hanoi discs     |
|                          |                                | ("shape()", "shapesize()")             |
+--------------------------+--------------------------------+----------------------------------------+
| "nim"                    | play the classical nim game    | turtles as nimsticks, event driven     |
|                          | with three heaps of sticks     | (mouse, keyboard)                      |
|                          | against the computer.          |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "paint"                  | super minimalistic drawing     | "onclick()"                            |
|                          | program                        |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "peace"                  | elementary                     | turtle: appearance and animation       |
+--------------------------+--------------------------------+----------------------------------------+
| "penrose"                | aperiodic tiling with kites    | "stamp()"                              |
|                          | and darts                      |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "planet_and_moon"        | simulation of gravitational    | compound shapes, "Vec2D"               |
|                          | system                         |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "rosette"                | a pattern from the wikipedia   | "clone()", "undo()"                    |
|                          | article on turtle graphics     |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "round_dance"            | dancing turtles rotating       | compound shapes, "clone()"             |
|                          | pairwise in opposite direction | "shapesize()", "tilt()",               |
|                          |                                | "get_shapepoly()", "update()"          |
+--------------------------+--------------------------------+----------------------------------------+
| "sorting_animate"        | visual demonstration of        | simple alignment, randomization        |
|                          | different sorting methods      |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "tree"                   | a (graphical) breadth first    | "clone()"                              |
|                          | tree (using generators)        |                                        |
+--------------------------+--------------------------------+----------------------------------------+
| "two_canvases"           | simple design                  | turtles on two canvases                |
+--------------------------+--------------------------------+----------------------------------------+
| "yinyang"                | another elementary example     | "circle()"                             |
+--------------------------+--------------------------------+----------------------------------------+

Have fun!
