matplotlib does not plot when named arguments are passed

Question

Can someone explain this behaviour?

import matplotlib.pyplot as plt
plt.plot(x=[0.05, 0.1, 0.15], y=[102, 211, 393])
plt.show()

import matplotlib.pyplot as plt
plt.plot([0.05, 0.1, 0.15], [102, 211, 393])
plt.show()

That is, without specifying x= and y= explicitly, pyplot works fine. However, this is different from the behaviour in the documentation. Well, the documentation does not explicitly use x= or y=, but it gives the signature of plot as plot(x, y). Therefore, named arguments should be permitted, and produce the same result, right?

Answer 1

I think the confusion comes from the difference in signatures. This is a python problem.

Consider

def func1(x,y):
    print(x,y)

def func2(*args):
    print(args)

You may call each of them with positional arguments.

func1(1,2)
func2(1,2)

You may also call the first function with named arguments.

func1(x=1, y=2)

However, you cannot call the second function with named arguments, because x and y are not defined.

func2(x=1, y=2)

results in an Error.

As seen from the documentation of plot, it uses the second way of defining the function,

matplotlib.pyplot.plot(*args, **kwargs)

I think the matplotlib documentation needs to assume some basic python understanding, but if there is something that can be done to clarify it, feel free to reach out with a suggestion on what to improve.