Check if two Python functions are equal

Question

I am wondering how I could check to see if two functions are the same. An example would be (lambda x: x) == (lambda y: y) evaluating to true. As far as I know, Python will check to see if the functions occupy the same location in memory, but not whether they have the same operation. I know it seems impractical to have that functionality.

Another solution would be some method I can run on a function to see what it contains or how it works. So a kind of (lambda x: x).what() that would return how the method works, maybe in a dictionary or something.

I would love an answer, but I doubt it's possible.

Answer 1

The one thing you could test for is code object equality:

>>> x = lambda x: x >>> y = lambda y: y >>> x.__code__.co_code '|\x00\x00S' >>> x.__code__.co_code == y.__code__.co_code True 

Here the bytecode for both functions is the same. You'll perhaps need to verify more aspects of the code objects (constants and closures spring to mind), but equal bytecode should equal the same execution path.

There are of course ways to create functions that return the same value for the same input, but with different bytecode; there are always more ways to skin a fish.