Python Method Arguments

At work, we have a library that we are installing using a Git Hash. This is an older library that has not been updated to use proper versioning and packaging.

The library has a change that needs to get pulled down but not all users are updating this library. The Goal of this is to check to see if a keyword argument has been added to a class method. The class looks kind of like this:

class MyFunkyClass:
    def __init__(self):
        pass

    def internal_method(self, arg1, arg2):
        pass

Our goal here is to check that arg2 is available as it was implemented.

I started looking around on how to do this, and came across the inspect module. If you look under the code Type, you can see the co_varnames and that it will give you:

tuple of names of arguments and local variables This is exactly what I’m looking for.

Let’s set up some code that sees if arg2 is an argument in MyFunkyClass.internal_method:

# Import the Class 
from funky import MyFunkyClass

# Get a pointer to the class method
method = getattr(MyFunkyClass, 'internal_method')

# Chceck if arg2 is an argument
assert 'arg2' in method.__code__.co_varnames

That’s it. Pretty simple.