How do you properly determine the current script directory in Python?

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How do you properly determine the current script directory in Python?

I would like to see what is the best way to determine the current script directory in Python.

I discovered that, due to the many ways of calling Python code, it is hard to find a good solution.

Here are some problems:

  • __file__ is not defined if the script is executed with exec, execfile
  • __module__ is defined only in modules

Use cases:

  • ./myfile.py
  • python myfile.py
  • ./somedir/myfile.py
  • python somedir/myfile.py
  • execfile('myfile.py') (from another script, that can be located in another directory and that can have another current directory.

I know that there is no perfect solution, but I’m looking for the best approach that solves most of the cases.

The most used approach is os.path.dirname(os.path.abspath(__file__)) but this really doesn’t work if you execute the script from another one with exec().

Warning

Any solution that uses current directory will fail, this can be different based on the way the script is called or it can be changed inside the running script.

Asked By: bogdan

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Answer #1:

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

is indeed the best you’re going to get.

It’s unusual to be executing a script with exec/execfile; normally you should be using the module infrastructure to load scripts. If you must use these methods, I suggest setting __file__ in the globals you pass to the script so it can read that filename.

There’s no other way to get the filename in execed code: as you note, the CWD may be in a completely different place.

Answered By: bobince

Answer #2:

If you really want to cover the case that a script is called via execfile(...), you can use the inspect module to deduce the filename (including the path). As far as I am aware, this will work for all cases you listed:

filename = inspect.getframeinfo(inspect.currentframe()).filename
path = os.path.dirname(os.path.abspath(filename))
Answered By: Sven Marnach

Answer #3:

#!/usr/bin/env python
import inspect
import os
import sys
def get_script_dir(follow_symlinks=True):
    if getattr(sys, 'frozen', False): # py2exe, PyInstaller, cx_Freeze
        path = os.path.abspath(sys.executable)
    else:
        path = inspect.getabsfile(get_script_dir)
    if follow_symlinks:
        path = os.path.realpath(path)
    return os.path.dirname(path)
print(get_script_dir())

It works on CPython, Jython, Pypy. It works if the script is executed using execfile() (sys.argv[0] and __file__ -based solutions would fail here). It works if the script is inside an executable zip file (/an egg). It works if the script is “imported” (PYTHONPATH=/path/to/library.zip python -mscript_to_run) from a zip file; it returns the archive path in this case. It works if the script is compiled into a standalone executable (sys.frozen). It works for symlinks (realpath eliminates symbolic links). It works in an interactive interpreter; it returns the current working directory in this case.

Answered By: jfs

Answer #4:

In Python 3.4+ you can use the simpler pathlib module:

from inspect import currentframe, getframeinfo
from pathlib import Path
filename = getframeinfo(currentframe()).filename
parent = Path(filename).resolve().parent

You can also use __file__ to avoid the inspect module altogether:

from pathlib import Path
parent = Path(__file__).resolve().parent
Answered By: Eugene Yarmash

Answer #5:

The os.path... approach was the ‘done thing’ in Python 2.

In Python 3, you can find directory of script as follows:

from pathlib import Path
cwd = Path(__file__).parents[0]
Answered By: Ron Kalian

Answer #6:

Just use os.path.dirname(os.path.abspath(__file__)) and examine very carefully whether there is a real need for the case where exec is used. It could be a sign of troubled design if you are not able to use your script as a module.

Keep in mind Zen of Python #8, and if you believe there is a good argument for a use-case where it must work for exec, then please let us know some more details about the background of the problem.

Answered By: wim

Answer #7:

Would

import os
cwd = os.getcwd()

do what you want? I’m not sure what exactly you mean by the “current script directory”. What would the expected output be for the use cases you gave?

Answered By: Will McCutchen

Answer #8:

First.. a couple missing use-cases here if we’re talking about ways to inject anonymous code..

code.compile_command()
code.interact()
imp.load_compiled()
imp.load_dynamic()
imp.load_module()
__builtin__.compile()
loading C compiled shared objects? example: _socket?)

But, the real question is, what is your goal – are you trying to enforce some sort of security? Or are you just interested in whats being loaded.

If you’re interested in security, the filename that is being imported via exec/execfile is inconsequential – you should use rexec, which offers the following:

This module contains the RExec class,
which supports r_eval(), r_execfile(),
r_exec(), and r_import() methods, which
are restricted versions of the standard
Python functions eval(), execfile() and
the exec and import statements. Code
executed in this restricted environment
will only have access to modules and
functions that are deemed safe; you can
subclass RExec add or remove capabilities as
desired.

However, if this is more of an academic pursuit.. here are a couple goofy approaches that you
might be able to dig a little deeper into..

Example scripts:

./deep.py

print ' >> level 1'
execfile('deeper.py')
print ' << level 1'

./deeper.py

print 't >> level 2'
exec("import sys; sys.path.append('/tmp'); import deepest")
print 't << level 2'

/tmp/deepest.py

print 'tt >> level 3'
print 'ttt I can see the earths core.'
print 'tt << level 3'

./codespy.py

import sys, os
def overseer(frame, event, arg):
    print "loaded(%s)" % os.path.abspath(frame.f_code.co_filename)
sys.settrace(overseer)
execfile("deep.py")
sys.exit(0)

Output

loaded(/Users/synthesizerpatel/deep.py)
>> level 1
loaded(/Users/synthesizerpatel/deeper.py)
    >> level 2
loaded(/Users/synthesizerpatel/<string>)
loaded(/tmp/deepest.py)
        >> level 3
            I can see the earths core.
        << level 3
    << level 2
<< level 1

Of course, this is a resource-intensive way to do it, you’d be tracing
all your code.. Not very efficient. But, I think it’s a novel approach
since it continues to work even as you get deeper into the nest.
You can’t override ‘eval’. Although you can override execfile().

Note, this approach only coveres exec/execfile, not ‘import’.
For higher level ‘module’ load hooking you might be able to use use
sys.path_hooks (Write-up courtesy of PyMOTW).

Thats all I have off the top of my head.

Answered By: synthesizerpatel

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