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pythonrelative-pathpython-packaging

How do I use a relative path in a Python module when the CWD has changed?

I have a Python module which uses some resources in a subdirectory of the module directory. After searching around on stack overflow and finding related answers, I managed to direct the module to the resources by using something like 

import os
os.path.join(os.path.dirname(__file__), 'fonts/myfont.ttf')

This works fine when I call the module from elsewhere, but it breaks when I call the module after changing the current working directory. The problem is that the contents of __file__ are a relative path, which doesn't take into account the fact that I changed the directory: 

>>> mymodule.__file__
'mymodule/__init__.pyc'
>>> os.chdir('..')
>>> mymodule.__file__
'mymodule/__init__.pyc'

How can I encode the absolute path in __file__, or barring that, how can I access my resources in the module no matter what the current working directory is? Thanks!

Solution

  • Store the absolute path to the module directory at the very beginning of the module:

    package_directory = os.path.dirname(os.path.abspath(__file__))

    Afterwards, load your resources based on this package_directory:

    font_file = os.path.join(package_directory, 'fonts', 'myfont.ttf')

    And after all, do not modify of process-wide resources like the current working directory. There is never a real need to change the working directory in a well-written program, consequently avoid os.chdir().