156 lines
4.9 KiB
TeX
156 lines
4.9 KiB
TeX
\section{\module{turtle} ---
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Turtle graphics for Tk}
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\declaremodule{standard}{turtle}
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\platform{Tk}
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\moduleauthor{Guido van Rossum}{guido@python.org}
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\modulesynopsis{An environment for turtle graphics.}
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\sectionauthor{Moshe Zadka}{moshez@zadka.site.co.il}
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The \module{turtle} module provides turtle graphics primitives, in both an
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object-oriented and procedure-oriented ways. Because it uses \module{Tkinter}
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for the underlying graphics, it needs a version of python installed with
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Tk support.
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The procedural interface uses a pen and a canvas which are automagically
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created when any of the functions are called.
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The \module{turtle} module defines the following functions:
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\begin{funcdesc}{degrees}{}
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Set angle measurement units to degrees.
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\end{funcdesc}
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\begin{funcdesc}{radians}{}
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Set angle measurement units to radians.
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\end{funcdesc}
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\begin{funcdesc}{reset}{}
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Clear the screen, re-center the pen, and set variables to the default
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values.
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\end{funcdesc}
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\begin{funcdesc}{clear}{}
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Clear the screen.
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\end{funcdesc}
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\begin{funcdesc}{tracer}{flag}
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Set tracing on/off (according to whether flag is true or not). Tracing
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means line are drawn more slowly, with an animation of an arrow along the
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line.
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\end{funcdesc}
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\begin{funcdesc}{forward}{distance}
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Go forward \var{distance} steps.
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\end{funcdesc}
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\begin{funcdesc}{backward}{distance}
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Go backward \var{distance} steps.
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\end{funcdesc}
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\begin{funcdesc}{left}{angle}
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Turn left \var{angle} units. Units are by default degrees, but can be
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set via the \function{degrees()} and \function{radians()} functions.
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\end{funcdesc}
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\begin{funcdesc}{right}{angle}
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Turn right \var{angle} units. Units are by default degrees, but can be
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set via the \function{degrees()} and \function{radians()} functions.
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\end{funcdesc}
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\begin{funcdesc}{up}{}
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Move the pen up --- stop drawing.
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\end{funcdesc}
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\begin{funcdesc}{down}{}
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Move the pen down --- draw when moving.
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\end{funcdesc}
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\begin{funcdesc}{width}{width}
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Set the line width to \var{width}.
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\end{funcdesc}
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\begin{funcdesc}{color}{s}
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\funclineni{color}{(r, g, b)}
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\funclineni{color}{r, g, b}
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Set the pen color. In the first form, the color is specified as a
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Tk color specification as a string. The second form specifies the
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color as a tuple of the RGB values, each in the range [0..1]. For the
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third form, the color is specified giving the RGB values as three
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separate parameters (each in the range [0..1]).
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\end{funcdesc}
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\begin{funcdesc}{write}{text\optional{, move}}
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Write \var{text} at the current pen position. If \var{move} is true,
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the pen is moved to the bottom-right corner of the text. By default,
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\var{move} is false.
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\end{funcdesc}
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\begin{funcdesc}{fill}{flag}
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The complete specifications are rather complex, but the recommended
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usage is: call \code{fill(1)} before drawing a path you want to fill,
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and call \code{fill(0)} when you finish to draw the path.
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\end{funcdesc}
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\begin{funcdesc}{circle}{radius\optional{, extent}}
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Draw a circle with radius \var{radius} whose center-point is
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\var{radius} units left of the turtle.
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\var{extent} determines which part of a circle is drawn: if
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not given it defaults to a full circle.
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If \var{extent} is not a full circle, one endpoint of the arc is the
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current pen position. The arc is drawn in a counter clockwise
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direction if \var{radius} is positive, otherwise in a clockwise
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direction. In the process, the direction of the turtle is changed
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by the amount of the \var{extent}.
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\end{funcdesc}
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\begin{funcdesc}{goto}{x, y}
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\funclineni{goto}{(x, y)}
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Go to co-ordinates \var{x}, \var{y}. The co-ordinates may be
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specified either as two separate arguments or as a 2-tuple.
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\end{funcdesc}
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This module also does \code{from math import *}, so see the
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documentation for the \refmodule{math} module for additional constants
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and functions useful for turtle graphics.
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\begin{funcdesc}{demo}{}
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Exercise the module a bit.
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\end{funcdesc}
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\begin{excdesc}{Error}
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Exception raised on any error caught by this module.
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\end{excdesc}
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For examples, see the code of the \function{demo()} function.
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This module defines the following classes:
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\begin{classdesc}{Pen}{}
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Define a pen. All above functions can be called as a methods on the given
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pen. The constructor automatically creates a canvas do be drawn on.
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\end{classdesc}
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\begin{classdesc}{RawPen}{canvas}
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Define a pen which draws on a canvas \var{canvas}. This is useful if
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you want to use the module to create graphics in a ``real'' program.
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\end{classdesc}
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\subsection{Pen and RawPen Objects \label{pen-rawpen-objects}}
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\class{Pen} and \class{RawPen} objects have all the global functions
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described above, except for \function{demo()} as methods, which
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manipulate the given pen.
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The only method which is more powerful as a method is
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\function{degrees()}.
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\begin{methoddesc}{degrees}{\optional{fullcircle}}
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\var{fullcircle} is by default 360. This can cause the pen to have any
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angular units whatever: give \var{fullcircle} 2*$\pi$ for radians, or
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400 for gradians.
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\end{methoddesc}
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