MF001: general-formatting

✨ Formatting 🛠️ Fixable

MF001: General formatting issues with the notebook format.

What it does

Examines the notebook serialization for structural violations such as:

• Missing or incorrect marimo import statements
• Improperly formatted cell definitions
• Missing app initialization code
• Incorrect file generation metadata

Why is this bad?

Format violations can prevent marimo from properly loading or executing notebooks. While these don't affect the Python code logic, formatting errors mark a deviation in the expected script structure, which can lead to unexpected behavior when run as a script, or when loading the notebook.

Examples

Problematic:

# Missing marimo import
@app.cell
def __():
    return


if __name__ == "__main__":
    app.run()

Solution:

import marimo

__generated_with = "0.1.0"
app = marimo.App()


@app.cell
def __():
    return


if __name__ == "__main__":
    app.run()

Note: Most format issues are automatically fixable with marimo check --fix.

References

• Understanding Errors
• File Format Documentation