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How To Fix “ImportError: No module named builtins” Error When Porting Python 2 to Python 3

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When you’re porting your application from Python 2 to Python 3, you may encounter the ImportError: No module named builtins error. This error arises because the builtins module, which is standard in Python 3, is not available in Python 2. This article will guide you through two effective solutions to resolve this issue.

Quick Answer

To fix the "ImportError: No module named builtins" error when porting Python 2 to Python 3, you can either install the future package, which provides support for the builtins module in Python 2, or modify your code to handle the import of builtins in a way that is compatible with both Python 2 and 3.

Understanding the Error

The ImportError: No module named builtins error is a common issue that developers face when they port their applications from Python 2 to Python 3 using the 2to3 tool. The 2to3 tool is a Python program that reads Python 2.x source code and applies a series of fixers to transform it into valid Python 3.x code. However, the builtins module, which is a standard module in Python 3, is not available in Python 2. As a result, when the converted code tries to import the builtins module in a Python 2 environment, it throws an ImportError.

Solution 1: Install the future package

One solution to this problem is to install the future package. The future package is a Python library designed to ease the migration from Python 2 to Python 3. It provides support for features that were introduced in Python 3 but are not available in Python 2, including the builtins module.

To install the future package, you can use the pip command. pip is a package manager for Python that allows you to install and manage additional packages that are not part of the Python standard library.

Here’s how you can install the future package:

sudo pip install future

In this command, sudo is used to run the command with root privileges, pip is the Python package installer, and install is the command to download and install a package. The future is the name of the package you want to install.

By installing the future package, the builtins module becomes available in Python 2, thereby resolving the ImportError.

Solution 2: Modify the code to handle the import

Another solution is to modify your code to handle the import of builtins in a way that is compatible with both Python 2 and 3. You can use a try-except block to attempt to import builtins and fall back to the Python 2 equivalent module __builtin__ if the import fails.

Here’s how you can modify your code:

try:
 import builtins
except ImportError:
 import __builtin__ as builtins

In this code, try and except are Python keywords used to catch and handle exceptions. The code under try is the block of code that will be attempted. If an error occurs while executing this block, the execution moves to the except block. Here, if the import of builtins fails, the code imports __builtin__ as builtins, ensuring that your code will work in both Python 2 and 3 environments.

By implementing one of these solutions, you should be able to fix the ImportError: No module named builtins issue when porting your Python 2 application to Python 3 using the 2to3 tool. Remember, porting an application from Python 2 to Python 3 is a significant task that requires careful planning and testing. Always make sure to thoroughly test your application in the new environment to ensure everything works as expected.

For more information on porting Python 2 code to Python 3, you can refer to the official Python documentation.

What is the purpose of the `builtins` module in Python?

The builtins module in Python provides a set of built-in functions, such as print() and len(), that are available for use without the need for any imports. It also contains other objects and exceptions that are fundamental to the language.

Can I use the `future` package for other Python 2 to Python 3 migration issues?

Yes, the future package is designed to help with various Python 2 to Python 3 migration issues. It provides additional compatibility layers and backports of Python 3 features to Python 2, making it easier to write code that is compatible with both versions.

Are there any other solutions to the `ImportError: No module named builtins` error?

Yes, there are alternative solutions to handle this error. One approach is to manually modify the code to replace the occurrences of builtins with __builtin__ in Python 2. However, this can be a tedious task, especially for large projects. Using the future package or the try-except block method mentioned in the article are generally more efficient and recommended solutions.

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