Resolving “No Module Named ‘regression_testing.common'” in Python Sphinx

Friendly Introduction to the Issue

Encountering errors like “No module named ‘regression_testing.common'” while using Sphinx for documentation generation in Python can be frustrating. Let’s unravel this issue together!

What You Will Learn

Discover how to troubleshoot and resolve the error where Sphinx fails to locate a specific module during the documentation creation process for your Python project.

Understanding the Problem and Finding a Solution

When working with Sphinx, a robust tool for crafting comprehensive documentation for Python projects, encountering module-related errors is not uncommon. The error message “No module named ‘regression_testing.common'” typically signifies that Python is unable to find the specified module. This can occur due to reasons such as incorrect installation, PYTHONPATH issues, or discrepancies in directory structures.

To tackle this problem effectively:

  1. Ensure your project’s structure aligns with Sphinx’s expectations.
  2. Verify and adjust PYTHONPATH settings if necessary.
  3. Explicitly specify module locations in Sphinx’s configuration file.


# Assuming your directory structure resembles:
# my_project/
# |-- docs/
# |   |--
# |   `-- ...
# `-- regression_testing/
#     `--

import os
import sys

sys.path.insert(0, os.path.abspath('../'))

# Copyright PHD

Add this snippet at the beginning of your file located in the docs directory of your project.


By modifying, which serves as Sphinx’s configuration file:

  • Import essential modules like os and sys.
  • Utilize os.path.abspath(‘../’) to compute an absolute path pointing one level above where resides.
  • Insert this path into sys.path to expand Python´┐Żs search path for modules, aiding in locating components like those from regression_testing.common.

Adjustments may be needed based on your actual directory layout.

  1. How do I install Sphinx?

  2. To install Sphinx, run:

  3. pip install sphinx
  4. # Copyright PHD
  5. What is PYTHONPATH?

  6. PYTHONPATH is an environment variable specifying additional locations for Python to search for modules during imports.

  7. How can I check my current PYTHONPATH?

  8. Execute:

  9. echo $PYTHONPATH  # Unix/Linux/macOS systems.
    echo %PYTHONPATH%  # Windows systems.
  10. # Copyright PHD
  11. Why does adjusting sys.path work?

  12. Modifying sys.path influences how Python searches for modules by adding directories to its search path dynamically.

  13. Can I specify multiple paths in sys.path?

  14. Yes, you can append multiple paths by calling sys.path.insert() with different paths.

  15. Is there an alternative method without changing

  16. You could manipulate PYTHONPATH before running sphinx-build; however, maintaining consistency across environments might become complex rapidly.


Navigating through missing module errors when utilizing Sphinx may appear daunting initially. However, understanding why these issues arise simplifies their resolution. The outlined approach offers a clear method of informing both Python and Sphinx about the precise location of our code concerning our documentation source files, smoothing out potential obstacles during document generation.

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