Python: import module without executing script

Question

I looked at a similar question but it does not really answer the question that I have. Say I have the following code (overly simplified to highlight only my question).

class A:
    def __init__(self,x):
        self.val = x

a = A(4)
print a.val

This code resides in a file someones_class.py. I now want to import and use class A in my program without modifying someones_class.py. If I do from someones_class import A, python would still execute the script lines in the file.

Question: Is there a way to just import class A without the last two lines getting executed?

I know about if __name__ == '__main__' thing but I do not have the option of modifying someones_class.py file as it is obtained only after my program starts executing.

Answer 1

This answer is just to demonstrate that it can be done, but would obviously need a better solution to ensure you are including the class(es) you want to include.

>>> code = ast.parse(open("someones_class.py").read())
>>> code.body.pop(1)
<_ast.Assign object at 0x108c82450>
>>> code.body.pop(1)
<_ast.Print object at 0x108c82590>
>>> eval(compile(code, '', 'exec'))
>>> test = A(4)
>>> test
<__main__.A instance at 0x108c7df80>

You could inspect the code body for the elements you want to include and remove the rest.

NOTE: This is a giant hack.

Answer 2

Nope, there's no way to prevent those extra lines from being executed. The best you can do is read the script and parse out the class -- using that to create the class you want.

This is likely way more work than you want to do, but, for the strong willed, the ast module might be helpful.