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gh-84464: Clarify how the signs of radius and extent affect turtle.circle() #157978

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gh-84464: Clarify how the signs of radius and extent affect turtle.circle() #157978

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9 changes: 6 additions & 3 deletions Doc/library/turtle.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -757,9 +757,12 @@ Turtle motion
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 direction of the
turtle is changed by the amount of *extent*.
position. If *radius* is negative, the center is to the right of the
turtle instead. The turtle moves forward along the arc if *extent* is
positive and backward if it is negative, so the arc is drawn
counterclockwise if *radius* and *extent* have the same sign, otherwise
clockwise. Finally the turtle turns left by *extent* if *radius* is
positive, otherwise right 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
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9 changes: 6 additions & 3 deletions Lib/turtle.py
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Expand Up @@ -2028,9 +2028,12 @@ def circle(self, radius, extent = None, steps = None):
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 direction of the turtle is changed by the amount of extent.
current pen position. If radius is negative, the center is to the
right of the turtle instead. The turtle moves forward along the
arc if extent is positive and backward if it is negative, so the
arc is drawn counterclockwise if radius and extent have the same
sign, otherwise clockwise. Finally the turtle turns left by extent
if radius is positive, otherwise right by extent.

As the circle is approximated by an inscribed regular polygon,
steps determines the number of steps to use. If not given,
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Documentation/2026-09-22-12-00-00.gh-issue-84464.tRtCrc.rst
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@StanFromIreland StanFromIreland Sep 23, 2026

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Docs changes don't need news entries.

Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Clarify the documentation of :func:`turtle.circle`: the sign of *extent*
also affects whether the arc is drawn clockwise or counterclockwise.
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