Ulrich Eckhardt wrote:
eric.frederich wrote:
Is there a way to set up environment variables in python itself
without having a wrapper script.
Yes, sure, you can set environment variables...
The wrapper script is now something like....
#!/bin/bash
export LD_LIBRARY_PATH="/some/thing/lib:$LD_LIBRARY_PATH"
export LD_LIBRARY_PATH="/another/thing/lib:$LD_LIBRARY_PATH"
export PATH="/some/thing/bin:$PATH"
export PATH="/another/thing/bin:$PATH"
python ./someScript.py
...but this won't work, I'm afraid.
LD_LIBRARY_PATH is for the program loader / dynamic linker under Linux. This
thing is what is invoked _before_ the program is started, any later
modifications to the environment are ignored.
In cases like yours I have sometimes written Python scripts that acted as
their own wrapper:
#!/usr/bin/env python
import os, sys
if 'LD_LIBRARY_PATH' in os.environ:
lib_path = os.environ['LD_LIBRARY_PATH']
if '/some/thing/lib' in lib_path and '/another/thing/lib' in lib_path:
pass
else:
os.environ['LD_LIBRARY_PATH'] += ':/some/thing/lib:/another/thing/lib'
os.execve(sys.argv[0], sys.argv, os.environ)
else:
os.environ['LD_LIBRARY_PATH'] = '/some/thing/lib:/another/thing/lib'
os.execve(sys.argv[0], sys.argv, os.environ)
os.environ['PATH'] = '/some/thing/bin:/another/thing/bin:' + os.environ['PATH']
# At this point, you can import a module that depends
# on LD_LIBRARY_PATH including /some/thing/lib
#
# Alternatively (and more clearly), you can replace the 'pass' above
# by that import statement
This code restarts Python if it has to modify os.environ['LD_LIBRARY_PATH'].
If you try to single-step this code under pdb, you'll get as far as the
os.execve() call. That call starts Python afresh, without a debugger.
In other words, if you need to use pdb, you'll have to set the environment
variables in the shell.
Similarly PATH, which tells the shell (e.g. bash) where to find executables.
If you need that to e.g. find 'python' itself, you're out of luck.
Otherwise, I believe Python itself doesn't use PATH, so you could set it
inside and any shells started from Python should pick it up.
You don't have to restart Python if you modify to os.environ['PATH'],
so that bit is easy.
Hope this helps,
-- HansM
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