pickle5 backport for older Python

Common errors

• ModuleNotFoundError: No module named 'pickle5'

  cause The `pickle5` library has not been installed in your Python environment.
  fix Install the library using pip: `pip install pickle5`

• ERROR: Package 'pickle5' requires a different Python version: 3.x.x but '>=3.5,<3.8' was specified.

  cause You are attempting to install `pickle5` on a Python version that is not supported by the library. `pickle5` is explicitly designed for Python 3.5-3.7.
  fix If your Python version is 3.8 or newer, `pickle5` is not needed; use the standard `import pickle` module instead. If you must use `pickle5`, you need to use a compatible Python environment (3.5-3.7).

Warnings

• breaking Installing `pickle5` on Python 3.8 or newer will fail due to `python_requires` constraints. If forcefully installed (e.g., via `pip install --no-deps` on an unsupported Python version), it can lead to subtle runtime issues, conflicts with the built-in `pickle` module, and unpredictable behavior, as Python 3.8+ already natively supports pickle protocol 5.
  Fix: Do not install `pickle5` on Python 3.8 or newer. Use the standard `import pickle` module, which includes protocol 5 support. If you have it installed, uninstall it: `pip uninstall pickle5`.
• gotcha The `pickle5` library is only necessary for Python versions 3.5, 3.6, and 3.7 to access pickle protocol 5. For Python 3.8 and all subsequent versions, protocol 5 is part of the standard `pickle` library and `pickle5` offers no additional functionality.
  Fix: Evaluate your project's Python version requirements. If you are targeting Python 3.8+, simply use `import pickle` and specify `protocol=5` if needed, or rely on the default highest protocol.
• deprecated The `pickle5` library is no longer actively maintained as its primary use case (backporting protocol 5) has been superseded by native Python versions. Relying on an unmaintained backport for critical serialization can introduce risks.
  Fix: It is highly recommended to upgrade your Python environment to 3.8 or newer to utilize the native `pickle` module's protocol 5 support and benefit from continued language updates and security patches.

Install

• pip install pickle5 Install on supported Python

Imports

• pickle5

  import pickle5

• dump
  wrong:

  from pickle import dump

  correct:

  from pickle5 import dump, load

  Use pickle5's functions directly for protocol 5 on older Pythons, not the standard library's pickle.

Quickstart

This example demonstrates how to use `pickle5` to dump and load a Python dictionary. `pickle5` automatically uses protocol 5 by default, offering improvements over earlier pickle protocols available in older Python versions.

import pickle5
import os

data = {'name': 'Alice', 'age': 30, 'city': 'New York'}

# Dump data using pickle5 (protocol 5 is default)
with open('data.pickle5', 'wb') as f:
    pickle5.dump(data, f)

print("Data successfully pickled to data.pickle5 using pickle5.")

# Load data using pickle5
with open('data.pickle5', 'rb') as f:
    loaded_data = pickle5.load(f)

print(f"Data successfully loaded: {loaded_data}")

# Clean up
os.remove('data.pickle5')