CODEWITHSUNDEEP
pythonmodule
zet4080
zet4080

Reputation: 55

How to ignore python modules during import?

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?

Upvotes: 2

Views: 10350

Answers (2)

Fnaxiom
Fnaxiom

Reputation: 396

Referring to "silently ignore the import", you can try this:

def TryImport(module_name):
    try:
        import module_name
    except ImportError:
        pass #or anything to log

Upvotes: 1

donkopotamus
donkopotamus

Reputation: 23216

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>)}

Upvotes: 2

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