Question

Is there a universal approach in Python, to find out the path to the file that is currently executing?

Failing approaches

path = os.path.abspath(os.path.dirname(sys.argv[0]))

This does not work if you are running from another Python script in another directory, for example by using execfile in 2.x.

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

I found that this doesn’t work in the following cases:

• py2exe doesn’t have a __file__ attribute, although there is a workaround
• When the code is run from IDLE using execute(), in which case there is no __file__ attribute
• On Mac OS X v10.6 (Snow Leopard), I get NameError: global name '__file__' is not defined

Test case

Directory tree

C:.
|   a.py
\---subdir
        b.py

Content of a.py

#! /usr/bin/env python
import os, sys

print "a.py: sys.argv[0]=", sys.argv[0]
print "a.py: __file__=", __file__
print "a.py: os.getcwd()=", os.getcwd()
print

execfile("subdir/b.py")

Content of subdir/b.py

#! /usr/bin/env python
import os, sys

print "b.py: sys.argv[0]=", sys.argv[0]
print "b.py: __file__=", __file__
print "b.py: os.getcwd()=", os.getcwd()
print

Output of python a.py (on Windows)

a.py: __file__= a.py
a.py: os.getcwd()= C:\zzz

b.py: sys.argv[0]= a.py
b.py: __file__= a.py
b.py: os.getcwd()= C:\zzz

Related (but these answers are incomplete)

• Find path to currently running file
• Path to current file depends on how I execute the program
• How can I know the path of the running script in Python?
• Change directory to the directory of a Python script

Answer 1

You can’t directly determine the location of the main script being executed. After all, sometimes the script didn’t come from a file at all. For example, it could come from the interactive interpreter or dynamically generated code stored only in memory.

However, you can reliably determine the location of a module, since modules are always loaded from a file. If you create a module with the following code and put it in the same directory as your main script, then the main script can import the module and use that to locate itself.

some_path/module_locator.py:

def we_are_frozen():
    # All of the modules are built-in to the interpreter, e.g., by py2exe
    return hasattr(sys, "frozen")

def module_path():
    encoding = sys.getfilesystemencoding()
    if we_are_frozen():
        return os.path.dirname(unicode(sys.executable, encoding))
    return os.path.dirname(unicode(__file__, encoding))

some_path/main.py:

import module_locator
my_path = module_locator.module_path()

If you have several main scripts in different directories, you may need more than one copy of module_locator.

Of course, if your main script is loaded by some other tool that doesn’t let you import modules that are co-located with your script, then you’re out of luck. In cases like that, the information you’re after simply doesn’t exist anywhere in your program. Your best bet would be to file a bug with the authors of the tool.