Resolving ModuleNotFoundError in Docker for Python Projects

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Troubleshooting Custom Python Module Not Found Errors in Docker

When working with Docker for your Python projects, it's not uncommon to encounter issues with custom modules not being found. This can be frustrating, especially when your code runs smoothly in a local environment. In this guide, we will explore a common scenario where a ModuleNotFoundError occurs and how to resolve it efficiently.

The Problem: Custom Python Module Not Found

Imagine you have structured your project as follows:

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This suggests that the custom module hasn't been installed properly within the container. We'll outline how to modify your setup so that it installs the module correctly.

Step 1: Use find_packages()

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with:

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And change it to:

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This tells setuptools to automatically find and include all the packages in your project.

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Step 2: Optional Modifications

Alternatively, you can specify your package explicitly like this:

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You can keep the package_dir line if you prefer, but it is not necessary since the folder name and package name are implicitly the same.

Step 3: Dockerfile Verification

No changes to the Dockerfile are needed. It should look like this:

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Testing Your Setup

Build your Docker image again with:

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Then, run your container and check if the module is recognized:

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From here, you can test your package:

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If you've followed these steps correctly, you should no longer encounter the ModuleNotFoundError.

Conclusion

Happy coding!