How Can I Efficiently Modify Environment Variables for External Commands in Python?

Modifying Environment Variables for External Commands in Python

To execute external commands with modified environment variables, many developers adopt an approach similar to the following:

import subprocess, os

# Copy the current environment
my_env = os.environ

# Append additional paths to the PATH variable
my_env["PATH"] += "/usr/sbin:/sbin"

# Execute the command with the modified environment
subprocess.Popen(my_command, env=my_env)

While this method works effectively, a more efficient approach exists by utilizing the os.environ.copy() function. This function creates a duplicate of the current environment, allowing you to make modifications without affecting the original.

import subprocess, os

# Create a copy of the current environment
my_env = os.environ.copy()

# Append additional paths to the PATH variable (using string interpolation for clarity)
my_env["PATH"] = f"/usr/sbin:/sbin:{my_env['PATH']}"

# Execute the command with the modified environment
subprocess.Popen(my_command, env=my_env)

This technique ensures that the modifications to the environment are scoped within the newly created copy and do not alter the original environment for the current process. It also promotes clearer code readability, especially when working with nested environments or complex path modifications.

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