[FIXED] How to ignore python modules during import?

Issue

During the build process of a Python application I need to ignore some imports (because these modules are created by the build process). It is a chicken-and-egg-question, that I can't resolve easily. So I thought I could use the import hook to do this like this:

class ImportBlocker(object):
    def __init__(self, *args):
        self.module_names = args

    def find_module(self, fullname, path=None):
        if fullname in self.module_names:
            return self
        return None

    def load_module(self, name):
        raise ImportError("%s is blocked and cannot be imported" % name)

import sys
sys.meta_path = [ImportBlocker('chickenlib')]

But because I raise an error the build process stop --- I just want to silently ignore the import ... returning "None" does not work, too. Is there a way to do this?

Solution

If you are working on Python 3.4 or greater than you can "silently ignore" an import by altering your example just slightly to implement an exec_module that will create an empty module.

class ImportBlocker(object):
    def __init__(self, *args):
        self.module_names = args

    def find_module(self, fullname, path=None):
        if fullname in self.module_names:
            return self
        return None

    def exec_module(self, mdl):
        # return an empty namespace
        return {}

Now:

>>> import sys
>>> sys.meta_path = [ImportBlocker('chickenlib')]

>>> # this will work fine
>>> import chickenlib

>>> # there is nothing useful in your imported module
>>> print(vars(chickenlib))
{'__doc__': None, '__package__': '', '__name__': 'chickenlib', '__loader__': <__main__.ImportBlocker object at 0x102b8c470>, '__spec__': ModuleSpec(name='chickenlib', loader=<__main__.ImportBlocker object at 0x102b8c470>)}

Answered By - donkopotamus

Answer Checked By - Robin (PHPFixing Admin)