How to Suppress the Generation of .pyc Files in Python?

Bypassing the Creation of .pyc Files

When executing Python code, .pyc files, containing the compiled bytecode, are often generated. However, certain scenarios may warrant the suppression of these files. This question explores ways to prevent their creation.

Solution

According to the official Python documentation ("What's New in Python 2.6 - Interpreter Changes"), one can suppress .pyc or .pyo file generation by using the -B switch. Alternatively, set the PYTHONDONTWRITEBYTECODE environment variable before running the interpreter. Python programs can also access this setting through the sys.dont_write_bytecode variable.

To execute your Python code without generating .pyc files, use the following command:

python -B prog.py

Python 3.2 Enhancement

For Python 3.2, a new feature was introduced: the __pycache__ subfolder. .pyc files are now stored in this subfolder instead of cluttering the source folders. (See "What's New in Python 3.2 - PYC Repository Directories" for more details.)

Performance Considerations

It's important to note that generating .pyc files is a performance optimization. By caching the compiled bytecode, it reduces the time required to execute the code subsequently. Disabling .pyc file generation (by setting PYTHONDONTWRITEBYTECODE=1) can negatively impact performance.

Additional Resources

For further information on .pyc files and their performance implications, refer to the following resources:

• "PEP 0304 -- Optimized Compilation" (Python 2): https://www.python.org/dev/peps/pep-0304/
• "PEP 3147 -- Optimized Compilation" (Python 3): https://www.python.org/dev/peps/pep-3147/
• "Performance Enhancements in Python" (GitHub): https://github.com/python/cpython

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