Question

One way to ensure that a method is called with a particular kwarg would be like:

def mymethod(self, *args, **kwargs):
    assert "required_field" in kwargs

Raising an AssertionError doesn’t seem like the most appropriate thing to do. Is there an agreed upon builtin exception to handle this with a nice error message?

More info: there are 3rd-party subclassing issues where *args and **kwargs kinda’ need to be passed so making “required_field” a positional argument is not really a good option.

Answer 1

>>> def foo(bar): pass
... 
>>> foo()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() missing 1 required positional argument: 'bar'

I’d just go with TypeError..