Importing a python module without actually executing it

Question

In the context of a complex application, I need to import user-supplied \'scripts\'. Ideally, a script would have

def init():
    blah

def execute():
    mo         


        

Answer 1

Here's a simpler (and more naive) alternative to the AST approach:

import sys
from imp import find_module, new_module, PY_SOURCE


EXPECTED = ("init", "execute", "cleanup")

def import_script(name):
    fileobj, path, description = find_module(name)

    if description[2] != PY_SOURCE:
        raise ImportError("no source file found")

    code = compile(fileobj.read(), path, "exec")

    expected = list(EXPECTED)
    for const in code.co_consts:
        if isinstance(const, type(code)) and const.co_name in expected:
            expected.remove(const.co_name)
    if expected:
        raise ImportError("missing expected function: {}".format(expected))

    module = new_module(name)
    exec(code, module.__dict__)
    sys.modules[name] = module
    return module

Keep in mind, this is a very direct way of doing it and circumvents extensions to Python's import machinery.