A pattern that keeps appearing in Python scripts, tutorials, and AI-generated code:

def main():
    do_stuff()

if __name__ == "__main__":
    main()

This is cargo-culted from C and Java, where a main() function is a syntactic requirement. Python has no such rule. The above is functionally identical to:

if __name__ == "__main__":
    do_stuff()

When def main() actually makes sense

There is one legitimate use case: when you need a named entry point for Python packaging. If your pyproject.toml defines a console script, it must reference a callable:

[project.scripts]
mytool = "mypackage.cli:main"

Here, def main() earns its place. But this is a specific packaging concern — not a general best practice for every script you write.

Why does this keep spreading?

• Language habits: Developers coming from C, Java, or Go carry the pattern into Python without questioning it.
• LLM training data: Models are trained on GitHub, which is full of this pattern, so they reproduce it automatically.
• Misunderstood testability: Some argue def main() makes code more testable. It doesn’t — if your logic is a monolith inside main(), it’s just as hard to test. Real testability comes from decomposing logic into focused, well-scoped functions.
• Cargo-culting tutorials: Many “professional Python” guides include it as boilerplate, implying it’s idiomatic when it’s really just familiar.

The Pythonic way

Write clean, decomposed functions. Use if __name__ == "__main__": as a lightweight guard when you need it. That’s it.

def process_data(data):
    ...

def save_results(results):
    ...

if __name__ == "__main__":
    data = load()
    results = process_data(data)
    save_results(results)