How to set your python path on Linux?

To set the PYTHONPATH on Linux to point Python to look in other directories for the module and package imports, you can use the export command. This is useful when you have custom modules or packages in non-standard locations.

Setting PYTHONPATH Temporarily

To add a directory to PYTHONPATH for the current terminal session ?

$ export PYTHONPATH=${PYTHONPATH}:${HOME}/foo

This command appends the foo directory to the existing PYTHONPATH without replacing its original value.

Example

Let's create a custom module and add its directory to PYTHONPATH ?

$ mkdir ~/mymodules
$ echo "def greet(): return 'Hello from custom module!'" > ~/mymodules/custom.py
$ export PYTHONPATH=${PYTHONPATH}:~/mymodules
$ python3 -c "import custom; print(custom.greet())"

Hello from custom module!

Setting PYTHONPATH Permanently

To make the change permanent, add the export command to your shell configuration file ?

# Add to ~/.bashrc or ~/.zshrc
echo 'export PYTHONPATH=${PYTHONPATH}:${HOME}/mymodules' >> ~/.bashrc
source ~/.bashrc

Checking Current PYTHONPATH

You can verify your PYTHONPATH setting using these methods ?

import sys
print("Python path directories:")
for path in sys.path:
    print(path)

Or from the command line ?

$ echo $PYTHONPATH

Best Practices

In most cases, you shouldn't modify PYTHONPATH. Consider these alternatives:

• Use virtual environments with pip install -e . for development
• Install packages properly using pip install
• Use sys.path.append() within your Python script for temporary additions

Alternative: Using sys.path

import sys
sys.path.append('/home/user/mymodules')
import custom
print(custom.greet())

Conclusion

While PYTHONPATH can be useful for custom module locations, it's often better to use virtual environments or proper package installation. Use PYTHONPATH sparingly and prefer more maintainable solutions.