Star imports

You're probably on this page because you just saw an error like this one:

marimo raises this error you attempt to use import *.

In this example, x was already defined, and the subsequent cell raised an error when we tried to run it. In your case, perhaps your variable is a loop variable (i), a dataframe (df), or a plot (fig, ax).

Why can't I use * imports?

Star imports are incompatible with marimo's git-friendly file format and reproducible reactive execution:

• marimo's Python file format stores code in functions, so notebooks can be imported as regular Python modules without executing all their code. But Python disallows import * everywhere except at the top-level of a module.
• Star imports would also silently add names to globals, which would be incompatible with reactive execution.

Even Python's official style guide discourages the use of import *, writing:

Wildcard imports (from <module> import *) should be avoided, as they make it unclear which names are present in the namespace, confusing both readers and many automated tools.

What do I get in return?

By accepting this constraint on imports, marimo makes your notebooks:

• reproducible, with a well-defined execution order, no hidden state, and no hidden bugs;
• executable as a script;
• interactive with UI elements that work without callbacks;
• shareable as a web app, with far better performance than streamlit.

As a bonus, you'll find that you end up with cleaner, reusable code.

How do I fix this error?

Fixing this error is simple: just import the module, and use . notation to access its members.

import math

math.pi

instead of

from math import *

pi