Installer avec Codex ou Claude Copiez ce prompt, collez-le dans Codex, Claude ou un autre assistant, puis laissez-le vérifier la page du skill et l'installer pour vous.
Une commande directe contourne le prompt de vérification. Examinez la source avant de l'exécuter.
Notice how the notebook is structured with functions can represent cell contents. Each cell is defined with the @app.cell decorator and the inputs/outputs of the function are the inputs/outputs of the cell. marimo usually takes care of the dependencies between cells automatically.
Running Marimo Notebooks
# Run as script (non-interactive, for testing)
uv run <notebook.py>
# Run interactively in browser
uv run marimo run <notebook.py>
# Edit interactively
uv run marimo edit <notebook.py>
Script Mode Detection
Use mo.app_meta().mode == "script" to detect CLI vs interactive:
Show all UI elements always. Only change the data source in script mode.
Sliders, buttons, widgets should always be created and displayed
In script mode, just use synthetic/default data instead of waiting for user input
Don't wrap everything in if not is_script_mode conditionals
Don't use try/except for normal control flow
Good Pattern
# Always show the widget@app.celldef_(ScatterWidget, mo):
scatter_widget = mo.ui.anywidget(ScatterWidget())
scatter_widget
return (scatter_widget,)
# Only change data source based on mode@app.celldef_(is_script_mode, make_moons, scatter_widget, np, torch):
if is_script_mode:
# Use synthetic data for testing
X, y = make_moons(n_samples=200, noise=0.2)
X_data = torch.tensor(X, dtype=torch.float32)
y_data = torch.tensor(y)
data_error = Noneelse:
# Use widget data in interactive mode
X, y = scatter_widget.widget.data_as_X_y
# ... process data ...return X_data, y_data, data_error
# Always show sliders - use their .value in both modes@app.celldef_(mo):
lr_slider = mo.ui.slider(start=0.001, stop=0.1, value=0.01)
lr_slider
return (lr_slider,)
# Auto-run in script mode, wait for button in interactive@app.celldef_(is_script_mode, train_button, lr_slider, run_training, X_data, y_data):
if is_script_mode:
# Auto-run with slider defaults
results = run_training(X_data, y_data, lr=lr_slider.value)
else:
# Wait for button clickif train_button.value:
results = run_training(X_data, y_data, lr=lr_slider.value)
return (results,)
State and Reactivity
Variables between cells define the reactivity of the notebook for 99% of the use-cases out there. No special state management needed. Don't mutate objects across cells (e.g., my_list.append()); create new objects instead. Avoid mo.state() unless you need bidirectional UI sync or accumulated callback state. See STATE.md for details.
Don't Guard Cells with if Statements
Marimo's reactivity means cells only run when their dependencies are ready. Don't add unnecessary guards:
# BAD - the if statement prevents the chart from showing@app.celldef_(plt, training_results):
if training_results: # WRONG - don't do this
fig, ax = plt.subplots()
ax.plot(training_results['losses'])
fig
return# GOOD - let marimo handle the dependency@app.celldef_(plt, training_results):
fig, ax = plt.subplots()
ax.plot(training_results['losses'])
fig
return
The cell won't run until training_results has a value anyway.
Don't Use try/except for Control Flow
Don't wrap code in try/except blocks unless you're handling a specific, expected exception. Let errors surface naturally.
# BAD - hiding errors behind try/except@app.celldef_(scatter_widget, np, torch):
try:
X, y = scatter_widget.widget.data_as_X_y
X = np.array(X, dtype=np.float32)
# ...except Exception as e:
returnNone, None, f"Error: {e}"# GOOD - let it fail if something is wrong@app.celldef_(scatter_widget, np, torch):
X, y = scatter_widget.widget.data_as_X_y
X = np.array(X, dtype=np.float32)
# ...
Only use try/except when:
You're handling a specific, known exception type
The exception is expected in normal operation (e.g., file not found)
You have a meaningful recovery action
Cell Output Rendering
Marimo only renders the final expression of a cell. Indented or conditional expressions won't render:
# BAD - indented expression won't render@app.celldef_(mo, condition):
if condition:
mo.md("This won't show!") # WRONG - indentedreturn# GOOD - final expression renders@app.celldef_(mo, condition):
result = mo.md("Shown!") if condition else mo.md("Also shown!")
result # This renders because it's the final expressionreturn
PEP 723 Dependencies
Notebooks created via marimo edit --sandbox have these dependencies added to the top of the file automatically but it is a good practice to make sure these exist when creating a notebook too:
When working on a notebook it is important to check if the notebook can run. That's why marimo provides a check command that acts as a linter to find common mistakes.
uvx marimo check <notebook.py>
Make sure these are checked before handing a notebook back to the user.
Important: you have a tendency to over-do variables with an underscore prefix. You should only apply this to one or two variables at most. Consider creating a new variable instead of prefixing entire cells in marimo.
api docs
If the user specifically wants you to use a marimo function, you can locally check the docs via:
uv --with marimo run python -c "import marimo as mo; help(mo.ui.form)"
tests
By default, marimo discovers and executes tests inside your notebook.
When the optional pytest dependency is present, marimo runs pytest on cells that
consist exclusively of test code - i.e. functions whose names start with test_.
If the user asks you to add tests, make sure to add the pytest dependency is added and that
there is a cell that contains only test code.
For more information on testing with pytest see PYTEST.md
Once tests are added, you can run pytest from the commandline on the notebook to run pytest.