Run-time Information

Your app should run in a bundle exactly as it does when run from source. However, you may need to learn at run-time whether the app is running from source, or is “frozen” (bundled). For example, you might have data files that are normally found based on a module’s __file__ attribute. That will not work when the code is bundled.

The PyInstaller bootloader adds the name frozen to the sys module. So the test for “are we bundled?” is:

import sys
if getattr( sys, 'frozen', False ) :
        # running in a bundle
else :
        # running live

When your app is running, it may need to access data files in any of three general locations:

  • Files that were bundled with it (see Adding Data Files).
  • Files the user has placed with the app bundle, say in the same folder.
  • Files in the user’s current working directory.

The program has access to several path variables for these uses.

Using __file__ and sys._MEIPASS

When your program is not frozen, the standard Python variable __file__ is the full path to the script now executing. When a bundled app starts up, the bootloader sets the sys.frozen attribute and stores the absolute path to the bundle folder in sys._MEIPASS. For a one-folder bundle, this is the path to that folder, wherever the user may have put it. For a one-file bundle, this is the path to the _MEIxxxxxx temporary folder created by the bootloader (see How the One-File Program Works).

Using sys.executable and sys.argv[0]

When a normal Python script runs, sys.executable is the path to the program that was executed, namely, the Python interpreter. In a frozen app, sys.executable is also the path to the program that was executed, but that is not Python; it is the bootloader in either the one-file app or the executable in the one-folder app. This gives you a reliable way to locate the frozen executable the user actually launched.

The value of sys.argv[0] is the name or relative path that was used in the user’s command. It may be a relative path or an absolute path depending on the platform and how the app was launched.

If the user launches the app by way of a symbolic link, sys.argv[0] uses that symbolic name, while sys.executable is the actual path to the executable. Sometimes the same app is linked under different names and is expected to behave differently depending on the name that is used to launch it. For this case, you would test os.path.basename(sys.argv[0])

On the other hand, sometimes the user is told to store the executable in the same folder as the files it will operate on, for example a music player that should be stored in the same folder as the audio files it will play. For this case, you would use os.path.dirname(sys.executable).

The following small program explores some of these possibilities. Save it as directories.py. Execute it as a Python script, then bundled as a one-folder app. Then bundle it as a one-file app and launch it directly and also via a symbolic link:

#!/usr/bin/python3
import sys, os
frozen = 'not'
if getattr(sys, 'frozen', False):
        # we are running in a bundle
        frozen = 'ever so'
        bundle_dir = sys._MEIPASS
else:
        # we are running in a normal Python environment
        bundle_dir = os.path.dirname(os.path.abspath(__file__))
print( 'we are',frozen,'frozen')
print( 'bundle dir is', bundle_dir )
print( 'sys.argv[0] is', sys.argv[0] )
print( 'sys.executable is', sys.executable )
print( 'os.getcwd is', os.getcwd() )

LD_LIBRARY_PATH / LIBPATH considerations

This environment variable is used to discover libraries, it is the library search path - on GNU/Linux and *BSD LD_LIBRARY_PATH is used, on AIX it is LIBPATH.

If it exists, PyInstaller saves the original value to *_ORIG, then modifies the search path so that the bundled libraries are found first by the bundled code.

But if your code executes a system program, you often do not want that this system program loads your bundled libraries (that are maybe not compatible with your system program) - it rather should load the correct libraries from the system locations like it usually does.

Thus you need to restore the original path before creating the subprocess with the system program.

env = dict(os.environ)  # make a copy of the environment
lp_key = 'LD_LIBRARY_PATH'  # for GNU/Linux and *BSD.
lp_orig = env.get(lp_key + '_ORIG')
if lp_orig is not None:
    env[lp_key] = lp_orig  # restore the original, unmodified value
else:
    # This happens when LD_LIBRARY_PATH was not set.
    # Remove the env var as a last resort:
    env.pop(lp_key, None)
p = Popen(system_cmd, ..., env=env)  # create the process