Setting Ld_Library_Path from Inside Python

Set LD_LIBRARY_PATH before importing in python

UPDATE: see the EDIT below.

I would use:

import os

os.environ['LD_LIBRARY_PATH'] = os.getcwd()  # or whatever path you want

This sets the LD_LIBRARY_PATH environment variable for the duration/lifetime of the execution of the current process only.

EDIT: it looks like this needs to be set before starting Python: Changing LD_LIBRARY_PATH at runtime for ctypes

So I'd suggest going with a wrapper .sh (or .py if you insist) script. Also, as @chepner pointed out, you might want to consider installing your .so files in a standard location (within the virtualenv).

See also Setting LD_LIBRARY_PATH from inside Python

Change current process environment's LD_LIBRARY_PATH

The reason

os.environ["LD_LIBRARY_PATH"] = ...

doesn't work is simple: this environment variable controls behavior of the dynamic loader (ld-linux.so.2 on Linux, ld.so.1 on Solaris), but the loader only looks at LD_LIBRARY_PATH once at process startup. Changing the value of LD_LIBRARY_PATH in the current process after that point has no effect (just as the answer to this question says).

You do have some options:

A. If you know that you are going to need xyz.so from /some/path, and control the execution of python script from the start, then simply set LD_LIBRARY_PATH to your liking (after checking that it is not already so set), and re-execute yourself. This is what Java does.

B. You can import /some/path/xyz.so via its absolute path before importing x.so. When you then import x.so, the loader will discover that it has already loaded xyz.so, and will use the already loaded module instead of searching for it again.

C. If you build x.so yourself, you can add -Wl,-rpath=/some/path to its link line, and then importing x.so will cause the loader to look for dependent modules in /some/path.

Changing LD_LIBRARY_PATH at runtime for ctypes

By the time a program such as Python is running, the dynamic loader (ld.so.1 or something similar) has already read LD_LIBRARY_PATH and won't notice any changes thereafter. So, unless the Python software itself evaluates LD_LIBRARY_PATH and uses it to build the possible path name of the library for dlopen() or an equivalent function to use, setting the variable in the script will have no effect.

Given that you say it doesn't work, it seems plausible to suppose that Python does not build and try all the possible library names; it probably relies on LD_LIBRARY_PATH alone.

How to set LD_LIBRARY_PATH for apache+wsgi website

Is the library required by a Python module extension you have compiled and installed? If it was, set LD_RUN_PATH environment variable to the directory the library is in when compiling and installing that Python module. That way the location is embedded in the Python module extension itself and you don't need LD_LIBRARY_PATH at run time.

The only other way to do it using environment variables is to set LD_LIBRARY_PATH in the startup scripts for Apache so that when Apache is started it is set as you require. This means fiddling with system startup scripts so is not ideal or always practical.

One final way which may work but isn't really that great of an idea and may not even work, is to use:

LoadFile "/usr/local/lib/libmylib.so"

in the Apache configuration. This will force linking of the specific library into Apache at startup, but depending on how the library is being used, this may not work.

Conda set LD_LIBRARY_PATH for env only

You can set environment variables when an environment is activated by editing the activate.d/env_vars.sh script. See here: https://conda.io/docs/user-guide/tasks/manage-environments.html#macos-and-linux

The key portions from that link are:

1. Locate the directory for the conda environment in your Terminal
   window, such as /home/jsmith/anaconda3/envs/analytics.

2. Enter that directory and create these subdirectories and
   files:

   cd /home/jsmith/anaconda3/envs/analytics
   mkdir -p ./etc/conda/activate.d
   mkdir -p ./etc/conda/deactivate.d
   touch ./etc/conda/activate.d/env_vars.sh
   touch ./etc/conda/deactivate.d/env_vars.sh
   

3. Edit ./etc/conda/activate.d/env_vars.sh as follows:

   #!/bin/sh
   
   export MY_KEY='secret-key-value'
   export MY_FILE=/path/to/my/file/
   

4. Edit ./etc/conda/deactivate.d/env_vars.sh as follows::

   #!/bin/sh
   
   unset MY_KEY
   unset MY_FILE
   

When you run conda activate analytics, the environment
variables MY_KEY and MY_FILE are set to the values you wrote into
the file. When you run conda deactivate, those variables are
erased.

CFFI how to avoid manual setting of LD_LIBRARY_PATH

Oh, I get it)

extra_link_args=['-Wl,-rpath=./lib'],

Big thanks to everyone!

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