Resolving ModuleNotFoundError When Importing Custom Classes in Python

Learn how to import custom classes in Python without running into `ModuleNotFoundError`. This guide provides effective solutions and best practices for structuring your Python modules.
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Resolving ModuleNotFoundError When Importing Custom Classes in Python

When working with Python, you may encounter issues when trying to import classes from your custom modules. A common error that you might run into is ModuleNotFoundError, indicating that Python can't locate the required module. This guide will introduce a common scenario where this issue arises and provide you with practical solutions to effectively solve it.

Understanding the Problem

Let's consider a project structure that looks like this:

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In this project, we have:

Here is the code present in each file:

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Providing a Solution

To fix this, we must ensure Python knows where to find our custom modules regardless of where the script is run. Here are some effective solutions to resolve the issue.

Solution -1: Use an __init__.py file

Create an __init__.py file in the helpers directory if you haven't done so already. This file can be empty but is necessary for Python to recognize the directory as a package.

Replace:

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With:

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or alternatively, use a relative import:

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Solution -2: Running the Script as a Module

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Best Practices for Importing Modules

Treat Python Scripts and Modules Differently: As demonstrated, ensure to differentiate between running scripts (which can be executed directly) and modules (which are meant to be imported).

Use __init__.py files: Make your directories packages by including __init__.py, which helps Python to find the modules inside.

Absolute and Relative Imports: Consider using absolute imports when you want clarity in the code structure and maintainability. Use relative imports when you want to keep your imports concise and structure within the package clear.

In conclusion, understanding how Python locates modules and classes allows you to structure your projects effectively, ensuring that scripts and modules work seamlessly together. By adhering to these practices, you minimize the likelihood of encountering import-related errors in the future.