How can I detect that my code is running in a Marimo notebook/app

[almarklein]

Is there a recommended way to detect that code is running in a Marimo environment? I have some code that needs to make a decision based on whether it runs in Marimo vs Jupyter vs desktop, etc.

I found IN_MARIMO = 'marimo' in sys.modules, but that can also happen when someone decided to import marimo for whatever reason.

[almarklein]

Or maybe (edited):

import __main__ as main_module

def is_in_marimo():
    try:
        main_module.__marimo__
        return True
    except AttributeError:
        pass

Added later: Or even shorter, thanks to @brisvag:

import __main__ as main_module

def is_in_marimo(): 
    return hasattr(main_module, '__marimo__'):

[manzt]

Great question! marimo has a public API for this — marimo.running_in_notebook(). It returns True only when code is actually executing inside the marimo runtime (edit or run mode), not just when marimo happens to be imported.

If you don't want to take a dependency on marimo, you can guard the import:

import sys

def is_in_marimo():
    if "marimo" not in sys.modules:
        return False
    return __import__("marimo").running_in_notebook()

[almarklein]

Awesome that this function exists, thanks!