Load python source code into function object

Question

I need to create a unit-test like framework for light-weight auto grading of single-function python assignments. I'd love to do something like the following:

test = """
def foo(x):
 return x * x
"""
compiled_module = magic_compile(test)
result = compiled_module.foo(3)
assert result == 9

Is there such a magic_compile function? The best I have so far is

exec(test)
result = getattr(sys.modules[__name__], 'foo')(3)

But this seems dangerous and unstable. This won't be run in production, so I'm not super-concerned about sandboxing and safety. Just wanted to make sure there wasn't a better solution I'm missing.

• nneonneo: Running an arbitrary function isn't any less dangerous than execing arbitrary code - you have to take the same precautions in both cases against malicious behaviour.
• thomas8wp: Yeah, I don't think there's an easy way to sandbox python as in this answer. I guess my larger concern is how to load it into an object that I can call.

Answer 1

In Python 3.x:

module = {}
exec(test, module)
assert module['foo'](3) == 9

module isn't a real Python module, it's just a namespace to hold the code's globals to avoid polluting your module's namespace.