{"id":9962,"library":"multiprocessing","title":"multiprocessing (Python 2.4/2.5 Backport)","description":"This PyPI package `multiprocessing` (version 2.6.2.1) is a backport of the standard library `multiprocessing` module, designed specifically for Python 2.4 and 2.5. It provides process-based parallelism for these very old, end-of-life Python versions. It is not intended for use with Python 2.6+ or Python 3.x, which include `multiprocessing` in their standard libraries.","status":"abandoned","version":"2.6.2.1","language":"en","source_language":"en","source_url":"https://sourceforge.net/projects/multiprocessing/","tags":["python2","backport","concurrency","abandoned","eol"],"install":[{"cmd":"pip install multiprocessing","lang":"bash","label":"For Python 2.4/2.5 only"}],"dependencies":[],"imports":[{"note":"This import path is consistent with the standard library version but applies to the backport.","symbol":"Process","correct":"from multiprocessing import Process"}],"quickstart":{"code":"# For Python 2.4/2.5 using the multiprocessing backport\nimport multiprocessing\nimport os\n\ndef worker_function(name):\n    print \"Worker %s: PID %s\" % (name, os.getpid())\n    return\n\nif __name__ == '__main__':\n    # The 'if __name__ == '__main__':` guard is crucial, especially on Windows.\n    process = multiprocessing.Process(target=worker_function, args=('Alice',))\n    process.start()\n    process.join()\n    print \"Main process: PID %s\" % os.getpid()\n","lang":"python","description":"A basic example demonstrating how to create and run a process using the backported `multiprocessing` module. This code is written for Python 2.x syntax."},"warnings":[{"fix":"For Python 3.x, use the built-in `multiprocessing` module directly without `pip install multiprocessing`.","message":"This PyPI package is a backport for Python 2.4/2.5 and is not compatible with Python 3.x. Attempting to use it will lead to syntax errors or unexpected behavior.","severity":"breaking","affected_versions":"2.x.x.x"},{"fix":"Do not install this package on Python 2.6+ or Python 3.x. The functionality is built into the standard library.","message":"Installing `multiprocessing` via pip in Python 2.6+, 2.7, or Python 3.x environments will result in an old, incompatible version being installed. This can cause conflicts with the standard library module or lead to confusion.","severity":"gotcha","affected_versions":"2.x.x.x"},{"fix":"Upgrade to a modern, supported Python version (Python 3.x) and utilize its built-in `multiprocessing` module.","message":"This package is a backport for Python 2.4/2.5, both of which are long past their end-of-life. The package is considered abandoned and should not be used for new development. Critical security vulnerabilities or bugs will not be addressed.","severity":"deprecated","affected_versions":"2.x.x.x"}],"env_vars":null,"last_verified":"2026-04-17T00:00:00.000Z","next_check":"2026-07-16T00:00:00.000Z","problems":[{"fix":"Run `pip install multiprocessing` in your Python 2.4/2.5 environment to install the backport.","cause":"The `multiprocessing` backport package is not installed in your Python 2.4/2.5 environment.","error":"ImportError: No module named multiprocessing"},{"fix":"Ensure you are running the code with a Python 2 interpreter. If migrating to Python 3, convert `print` statements to `print()` functions.","cause":"You are attempting to run Python 2.x code (using `print` as a statement) with a Python 3 interpreter.","error":"SyntaxError: Missing parentheses in call to 'print'"},{"fix":"Ensure all code that creates child processes is encapsulated within an `if __name__ == '__main__':` block in your main script.","cause":"The `multiprocessing` module (both backport and standard library) requires the entry point of the script to be protected by an `if __name__ == '__main__':` block, especially on Windows.","error":"RuntimeError: An attempt has been made to start a new process before the current process has finished its bootstrapping phase."},{"fix":"import multiprocessing\n\n# Define functions at the module level\ndef my_picklable_function(data):\n    return data * 2\n\nif __name__ == '__main__':\n    p = multiprocessing.Process(target=my_picklable_function, args=(5,))\n    p.start()\n    p.join()","cause":"Objects (especially functions defined locally or complex custom objects) passed between processes must be picklable, but an unpicklable object was used.","error":"PicklingError: Can't pickle <type 'function'>: attribute lookup __builtin__.function failed"},{"fix":"import os\nimport multiprocessing\n\ndef get_cpu_count_manual():\n    if os.name == 'posix':\n        try: return os.sysconf('SC_NPROCESSORS_ONLN')\n        except (AttributeError, ValueError): pass\n    return 1 # Fallback if specific method fails or for other OS\n\nnum_cpus = get_cpu_count_manual()\nprint('Detected CPUs:', num_cpus)","cause":"The `multiprocessing.cpu_count()` function was introduced in Python 2.6 (and the standard library `multiprocessing`) and is not available in the Python 2.4/2.5 backport.","error":"AttributeError: 'module' object has no attribute 'cpu_count'"}]}