How to set environment variables in Python

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  1. Setting environment variables in Python can be achieved in several ways, depending on whether you want to set them temporarily (for the current process) or permanently (system-wide). Below are the methods to set environment variables in Python:

    1. Temporarily Within a Python Script

    You can set environment variables for the current process using the os module, which will only affect the program's environment during its execution time.

    import os
    
    # Set an environment variable
    os.environ['MY_VARIABLE'] = 'value'
    
    # Get the value of an environment variable
    value = os.getenv('MY_VARIABLE', 'default_value')
    print(value)
    

    2. For the Current Session in a Terminal

    Setting an environment variable for the duration of your current terminal session can be done using the command line, not directly through Python. The method depends on your operating system's shell.

    • On Windows (Command Prompt):

      set MY_VARIABLE=value
      
    • On Linux/macOS (Bash Shell):

      export MY_VARIABLE=value
      

    3. Permanently for All Future Terminal Sessions and Applications

    To set an environment variable permanently, you need to add it to your system's environment configuration files, which varies by operating system.

    • On Windows: You can set environment variables permanently through the System Properties -> Environment Variables dialog, or by using the setx command:

      setx MY_VARIABLE "value"
      
    • On Linux/macOS: Add the export command to your shell's profile script (e.g., ~/.bash_profile, ~/.bashrc, ~/.zshrc):

      echo 'export MY_VARIABLE="value"' >> ~/.bash_profile
      

      Then, reload the profile with source ~/.bash_profile.

    4. Using Python to Permanently Set Environment Variables

    Permanently setting environment variables system-wide from within a Python script is not straightforward because it involves modifying system files or the Windows registry. Typically, you would use the methods mentioned above and possibly automate them with Python scripts that manipulate the relevant files or registry entries directly. However, due to the complexity and risks involved in modifying system files or the registry, it's recommended to manually set these variables or use platform-specific scripts outside of Python for this purpose.

    In summary, setting environment variables temporarily can easily be done within a Python script using the os module. For permanent changes, it's more reliable to use system-specific methods outside of Python.

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