PIP showing ModuleNotFoundError while upgrade/downgrade

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Summary

The issue at hand is a ModuleNotFoundError when attempting to downgrade pip to version 18.1. This error is encountered despite uninstalling and reinstalling urllib3 and requests. The command used to trigger this error is python -m pip install pip==18.1, resulting in the error message ModuleNotFoundError: No module named 'pip._vendor.urllib3.packages.six.moves'.

Root Cause

The root cause of this issue can be attributed to several factors:

  • Incompatible dependencies: The version of urllib3 or requests might be incompatible with pip version 18.1.
  • Corrupted pip installation: The pip installation might be corrupted, leading to missing modules.
  • Version conflicts: Conflicts between different versions of pip and its dependencies.

Why This Happens in Real Systems

This issue occurs in real systems due to:

  • Dependency management: Poor dependency management can lead to version conflicts and incompatible dependencies.
  • Package corruption: Corruption of packages during installation or upgrade can cause missing modules.
  • Environment issues: Issues with the Python environment, such as multiple Python versions or corrupted environment variables, can contribute to this problem.

Real-World Impact

The real-world impact of this issue includes:

  • Failed deployments: Inability to deploy applications due to pip installation issues.
  • Development delays: Delays in development due to pip version conflicts and missing modules.
  • System instability: Potential system instability caused by corrupted pip installations.

Example or Code (if necessary and relevant)

import pip
print(pip.__version__)

This code snippet can be used to verify the current version of pip.

How Senior Engineers Fix It

Senior engineers fix this issue by:

  • Reinstalling pip: Reinstalling pip using the official installation script.
  • Upgrading dependencies: Upgrading urllib3 and requests to compatible versions.
  • Verifying environment: Verifying the Python environment and ensuring that all dependencies are correctly installed.

Why Juniors Miss It

Junior engineers might miss this issue due to:

  • Lack of experience: Limited experience with pip and its dependencies.
  • Insufficient knowledge: Inadequate knowledge of Python environment management and dependency resolution.
  • Inadequate testing: Inadequate testing of pip installations and dependencies.