The following exception message seems misleading, or at least not obvious:

>>> def f(a,b,c): pass
... 
>>> f(c=0,a=0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: f() takes exactly 3 non-keyword arguments (1 given)

Why "1 given" ? One could argue for either 0 or 2 given arguments but I fail to see how 1 is a reasonable answer.