[issue40283] Documentation of turtle.circle()
New submission from guchao <guchao2000@163.com>: refer to circle() in the url: https://docs.python.org/2/library/turtle.html#turtle.circle [current] ... Draw the arc in counterclockwise direction if radius is positive, otherwise in clockwise direction. [suggestion] ... Draw the arc in counterclockwise direction if extent is positive, otherwise in clockwise direction. [explanation] It should be "extent" , instead of "radius", that affects the direction. ---------- assignee: docs@python components: Documentation messages: 366401 nosy: docs@python, guchao priority: normal severity: normal status: open title: Documentation of turtle.circle() type: resource usage _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40283> _______________________________________
Terry J. Reedy <tjreedy@udel.edu> added the comment: It would be bizarre if the current doc were correct, but have you verified by experiment that the change is correct? The patch itself would be trivial, hence the keyword addition. PR author can request that I review. ---------- keywords: +easy, newcomer friendly nosy: +terry.reedy stage: -> needs patch type: resource usage -> behavior versions: +Python 3.7, Python 3.8, Python 3.9 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40283> _______________________________________
Cajetan Rodrigues <caje731@gmail.com> added the comment: When I checked, I found the following: turtle.circle(50, 50) # counter-clockwise turtle.circle(-50, -50) # counter-clockwise turtle.circle(-50, 50) # clockwise turtle.circle(50, -50) # clockwise So it seems both radius and extent need to be of the same signage to effect a counter-clockwise draw. However, for the 2 cases where extent is negative, the draw happens through the turtle's tail rather than the head. Looks weird. ---------- nosy: +cajetan.rodrigues _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40283> _______________________________________
Florian Dahlitz <f.dahlitz@outlook.de> added the comment: I tested it and can confirm the findings from @cajetan.rodrigues. However, this does not seem to be _not_ documented. The documentation clearly states that using a positive value for radius results in a counter-clockwise direction, whereas a negative number results in a clockwise direction. This is true. Now, let's have a look at using radius _together_ with extent, which is not (clearly) documented as this point. Using a positive value results in the same direction, but in a not full drawn circle. This seems intuitive and is documented: 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. Using a negative value changes the direction of radius, which does also seem reasonable and intuitive. My suggestion is not to replace "radius" by "extent" as suggested by @guchao as it is IMHO wrong. But I agree that it would be good to leave a note there or to add examples demonstrating the behaviour of different (signed) values of radius and extent, so the intent and behaviour is clearly documented. ---------- nosy: +DahlitzFlorian _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40283> _______________________________________
Change by Frank Henigman <fjhenigman@gmail.com>: ---------- nosy: +fjh _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40283> _______________________________________
Change by Mike Weilgart <mikeweilgart@gmail.com>: ---------- keywords: +patch nosy: +Weildcard nosy_count: 6.0 -> 7.0 pull_requests: +20107 stage: needs patch -> patch review pull_request: https://github.com/python/cpython/pull/20928 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue40283> _______________________________________
participants (6)
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Cajetan Rodrigues -
Florian Dahlitz
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Frank Henigman
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guchao
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Mike Weilgart
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Terry J. Reedy