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MR004: private-import-alias

⚠️ Runtime ❌ Not Fixable

MR004: Import aliased to a private (underscore-prefixed) name.

What it does

Scans import statements for an explicit as alias whose bound name starts with an underscore. This pattern is an undesirable but common workaround for marimo's global redefinition restriction with little tangible payoff.

Why is this bad?

Aliasing an import to a private name doesn't give the benefits users expect from it:

  • Imported modules are registered in sys.modules regardless of the name they're bound to, so marimo's private-variable cleanup doesn't free any extra memory.
  • Common imports like numpy, pandas, and os are usually needed in multiple cells, and giving them a private name defeats reuse while adding clutter.

If the goal is to avoid the import polluting cell-to-cell dependencies, the fix is a setup cell, or import only cell instead. Setup cells run once, ahead of every other cell, while import only cells don't trigger re-execution of dependent cells (imports resolve independently of the notebook's reactive dataflow). Both of these approaches are preferable to aliasing imports to private names. You may even consider import only setup cells!

Examples

Problematic: 

import os as _os

_os.listdir(".")


import os as _os

_os.getcwd()

Problematic: 

from collections import OrderedDict as _OrderedDict

Solution: 

# In the notebook's setup cell
# or any import only cell.
import os
from collections import OrderedDict


os.listdir(".")

os.getcwd()

References