How to retrieve a module's path?

Question

I want to detect whether module has changed. Now, using inotify is simple, you just need to know the directory you want to get notifications from.

How do I retrieve

Answer 1

As the other answers have said, the best way to do this is with __file__ (demonstrated again below). However, there is an important caveat, which is that __file__ does NOT exist if you are running the module on its own (i.e. as __main__).

For example, say you have two files (both of which are on your PYTHONPATH):

#/path1/foo.py
import bar
print(bar.__file__)

and

#/path2/bar.py
import os
print(os.getcwd())
print(__file__)

Running foo.py will give the output:

/path1        # "import bar" causes the line "print(os.getcwd())" to run
/path2/bar.py # then "print(__file__)" runs
/path2/bar.py # then the import statement finishes and "print(bar.__file__)" runs

HOWEVER if you try to run bar.py on its own, you will get:

/path2                              # "print(os.getcwd())" still works fine
Traceback (most recent call last):  # but __file__ doesn't exist if bar.py is running as main
  File "/path2/bar.py", line 3, in 
    print(__file__)
NameError: name '__file__' is not defined 

Hope this helps. This caveat cost me a lot of time and confusion while testing the other solutions presented.