turtle.dot(size="blue") has a weird behaviour

Bug description:

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

    Parameters:

            size – an integer >= 1 (if given)

            color – a colorstring or a numeric color tuple

However, turtle.dot(size="blue") doesn't raise an exception. Instead of this, the color is changed to blue.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Intentional, however:

cpython/Lib/turtle.py

Lines 3501 to 3503 in 4ac16dd

    
           if isinstance(size, (str, tuple)): 
        
               color = self._colorstr(size) 
        
               size = self._pensize + max(self._pensize, 4)

So I shall mark this as a feature.

Yeah, this is the runtime code:

    def dot(self, size=None, *color):
        """Draw a dot with diameter size, using color.

        Optional arguments:
        size -- an integer >= 1 (if given)
        color -- a colorstring or a numeric color tuple

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

        Example (for a Turtle instance named turtle):
        >>> turtle.dot()
        >>> turtle.fd(50); turtle.dot(20, "blue"); turtle.fd(50)
        """
        if not color:
            if isinstance(size, (str, tuple)):
                color = self._colorstr(size)
                size = self._pensize + max(self._pensize, 4)
            else:
                color = self._pencolor
                if not size:
                    size = self._pensize + max(self._pensize, 4)
        else:
            if size is None:
                size = self._pensize + max(self._pensize, 4)
            color = self._colorstr(color)

This is the corresponding type hint in typeshed:

    @overload
    def dot(self, size: int | _Color | None = None) -> None: ...
    @overload
    def dot(self, size: int | None, color: _Color, /) -> None: ...
    @overload
    def dot(self, size: int | None, r: float, g: float, b: float, /) -> None: ...

And this is what the docs state (https://docs.python.org/3/library/turtle.html#turtle.dot):

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

I dont think there is a way to achieve the current desired behaviour without this

Intentional, however:

cpython/Lib/turtle.py

Lines 3501 to 3503 in 4ac16dd
if isinstance(size, (str, tuple)):
color = self._colorstr(size)
size = self._pensize + max(self._pensize, 4)

So I shall mark this as a feature.

I saw this. The problem seems to be on 3502 line.

After, the color variable will be used in

cpython/Lib/turtle.py

Lines 3520 to 3523 in 4ac16dd

    
           self.pendown() 
        
           self.pensize(size) 
        
           self.pencolor(color) 
        
           self.forward(0)

I think we just need to erase the 3502 line.

If you want to allow all three of these

turtle.dot(3)
turtle.dot("blue")
turtle.dot(size=3)

then i dont think there is a way to NOT have

turtle.dot(size="blue")

If you want to allow all three of these
turtle.dot(3)
turtle.dot("blue")
turtle.dot(size=3)
then i dont think there is a way to NOT have
turtle.dot(size="blue")

I got your point.

Is it possible to identify if an argument was passed by position or by name?

Is it possible to identify if an argument was passed by position or by name?

In general, no, such information is not preserved. We could convert it to dot(*args, **kwargs) and we could then distinguish positional vs keyword, but implementing it with all of the required additional handling is quite messy, and not worth the additional complexity in this case IMO.

What about having an ad-hoc wrapper which could use *args and **kwargs (and functools.wraps to preserve the original signature), and then error on a non-numeric "size" passed by name?

I think that the simplest way to get rid of such weird behavior is to forbid passing the size argument by keyword. Yes, this is a breaking change, and normally we would need to add a complicated code that emits a deprecation warning. But it is unlikely that many code will be broke -- there is no benefit of passing size by keyword, especially if you cannot pass color by keyword.

On other hand, if nobody passes the size argument by keyword, this change would fix no code. This would be mostly cosmetic change.

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turtle.dot(size="blue") has a weird behaviour #141062

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	if isinstance(size, (str, tuple)):
	color = self._colorstr(size)
	size = self._pensize + max(self._pensize, 4)

	self.pendown()
	self.pensize(size)
	self.pencolor(color)
	self.forward(0)

turtle.dot(size="blue") has a weird behaviour #141062

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Bug description:

CPython versions tested on:

Operating systems tested on:

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StanFromIreland commented on Nov 5, 2025

JanEricNitschke commented on Nov 5, 2025

adorilson commented on Nov 5, 2025

JanEricNitschke commented on Nov 5, 2025

adorilson commented on Nov 5, 2025

StanFromIreland commented on Nov 5, 2025

jsbueno commented on Nov 5, 2025

serhiy-storchaka commented on Nov 6, 2025

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