TypeError: got multiple values for argument

I had the same problem that is really easy to make, but took me a while to see through.

I had copied the declaration to where I was using it and had left the 'self' argument there, but it took me ages to realise that.

I had

self.myFunction(self, a, b, c='123')

but it should have been

self.myFunction(a, b, c='123')

This happens when a keyword argument is specified that overwrites a positional argument. For example, let's imagine a function that draws a colored box. The function selects the color to be used and delegates the drawing of the box to another function, relaying all extra arguments.

def color_box(color, *args, **kwargs):
    painter.select_color(color)
    painter.draw_box(*args, **kwargs)

Then the call

color_box("blellow", color="green", height=20, width=30)

will fail because two values are assigned to color: "blellow" as positional and "green" as keyword. (painter.draw_box is supposed to accept the height and width arguments).

This is easy to see in the example, but of course if one mixes up the arguments at call, it may not be easy to debug:

# misplaced height and width
color_box(20, 30, color="green")

Here, color is assigned 20, then args=[30] and color is again assigned "green".