subprocess32 Backport for Python 2

Warnings

• breaking The `subprocess32` library is explicitly end-of-life (EOL) along with Python 2. This means no further development, bug fixes, or security updates are planned. Relying on it in new projects is strongly discouraged.
  Fix: Migrate applications from Python 2 to Python 3. Python 3's built-in `subprocess` module provides the same or superior functionality and thread safety.
• gotcha `subprocess32` is primarily designed for POSIX systems (Linux, macOS) and has not been tested or fully supported on Windows or other non-POSIX platforms. Attempts to install or use it on Windows may lead to compilation errors (e.g., missing `unistd.h`) or unexpected behavior.
  Fix: Avoid using `subprocess32` on Windows. For cross-platform Python 2 code, consider a conditional import that uses the native `subprocess` module on Windows, or use alternative process management libraries that explicitly support Windows.
• gotcha While `subprocess32` backports `timeout` support (from Python 3.3) and the `run()` API (from Python 3.5), other features and APIs are 'frozen at the 3.2 level'. This means `subprocess32` is not a complete, feature-for-feature replica of the latest Python 3 `subprocess` module.
  Fix: Always consult Python 3.2 documentation for `subprocess` when using `subprocess32`, and explicitly check the `subprocess32` GitHub README for details on backported features like `run()` and `timeout`. Do not assume full parity with newer Python 3 versions.
• gotcha The primary motivation for `subprocess32` was to address race conditions and improve thread-safety in Python 2.x's native `subprocess` module on POSIX systems, particularly in multi-threaded applications. Not using `subprocess32` (i.e., using the built-in `subprocess` on Python 2) can lead to unreliable behavior and crashes when processes are spawned in threaded contexts.
  Fix: Always use `subprocess32` (via the conditional import pattern) when running Python 2.x code that spawns subprocesses, especially in threaded environments. For new development, migrate to Python 3.

Install

• pip install subprocess32 Install on Python 2.x

Imports

• subprocess

  import os, sys
  
  if sys.version_info[0] < 3:
      try:
          import subprocess32 as subprocess
      except ImportError:
          import subprocess
  else:
      import subprocess

  On Python 2, directly importing `subprocess` (the built-in module) can lead to thread-safety issues and lacks modern features. The recommended pattern is to conditionally import `subprocess32` to leverage its fixes and features on Python 2, falling back to the built-in `subprocess` if `subprocess32` isn't available, and using the standard `subprocess` on Python 3.

Quickstart

This quickstart demonstrates the recommended import pattern and basic usage of the `subprocess.run()` function, which was backported from Python 3.5. It includes capturing output, handling errors with `check=True`, and setting a timeout. Note that `text=True` is an alias for `universal_newlines=True` within `subprocess32` for Python 2.

import os, sys

# Recommended import pattern for cross-version compatibility
if sys.version_info[0] < 3:
    try:
        import subprocess32 as subprocess
    except ImportError:
        print("Warning: subprocess32 not found, using native subprocess module.")
        import subprocess
else:
    import subprocess

try:
    # Execute a simple command
    result = subprocess.run(
        ['echo', 'Hello, subprocess32!'],
        capture_output=True,
        text=True, # In Python 2, this maps to universal_newlines=True
        check=True,
        timeout=5
    )
    print("STDOUT:", result.stdout.strip())
    print("STDERR:", result.stderr.strip())

    # Example with error
    subprocess.run(['false'], check=True)
except subprocess.CalledProcessError as e:
    print(f"Command failed with exit code {e.returncode}")
except subprocess.TimeoutExpired:
    print("Command timed out")
except Exception as e:
    print(f"An unexpected error occurred: {e}")