Recipes#

This page includes code snippets or “recipes” for a variety of common tasks. Use them as building blocks or examples when making your own notebooks.

In these recipes, each code block represents a cell.

Control Flow#

Show an output conditionally#

Use cases. Hide an output until a condition is met (e.g., until algorithm parameters are valid), or show different outputs depending on the value of a UI element or some other Python object

Recipe.

Use an if expression to choose which output to show.

# condition is a boolean, True of False
condition = True
"condition is True" if condition else None

Run a cell on a timer#

Use cases.

Load new data periodically, and show updated plots or other outputs. For example, in a dashboard monitoring a training run, experiment trial, real-time weather data, …
Run a job periodically

Recipe.

Import packages

import marimo as mo

Create a mo.ui.refresh timer that fires once a second:

refresh = mo.ui.refresh(default_interval="1s")
# This outputs a timer that fires once a second
refresh

Reference the timer by name to make this cell run once a second

import random

# This cell will run once a second!
refresh

mo.md("#" + "🍃" * random.randint(1, 10))

Require form submission before sending UI value#

Use cases. UI elements automatically send their values to the Python when they are interacted with, and run all cells referencing the elements. This makes marimo notebooks responsive, but it can be an issue when the downstream cells are expensive, or when the input (such as a text box) needs to be filled out completely before it is considered valid. Forms let you gate submission of UI element values on manual confirmation, via a button press.

Recipe.

Import packages

import marimo as mo

Create a submittable form.

form = mo.ui.text(label="Your name").form()
form

Get the value of the form.

form.value

Stop execution of a cell and its descendants#

Use cases. For example, don’t run a cell or its descendants if a form is unsubmitted.

Recipe.

Import packages

import marimo as mo

Create a submittable form.

form = mo.ui.text(label="Your name").form()
form

Use mo.stop to stop execution when the form is unsubmitted.

mo.stop(form.value is None, mo.md("Submit the form to continue"))

mo.md(f"Hello, {form.value}!")

Grouping UI elements together#

Create an array of UI elements#

Use cases. In order to synchronize UI elements between the frontend and backend (Python), marimo requires you to assign UI elements to global variables. But sometimes you don’t know the number of elements to make until runtime: for example, maybe you want o make a list of sliders, and the number of sliders to make depends on the value of some other UI element.

You might be tempted to create a Python list of UI elements, such as l = [mo.ui.slider(1, 10) for i in range(number.value)]: however, this won’t work, because the sliders are not bound to global variables.

For such cases, marimo provides the “higher-order” UI element mo.ui.array, which lets you make a new UI element out of a list of UI elements: l = mo.ui.array([mo.ui.slider(1, 10) for i in range(number.value)]). The value of an array element is a list of the values of the elements it wraps (in this case, a list of the slider values). Any time you interact with any of the UI elements in the array, all cells referencing the array by name (in this case, “l”) will run automatically.

Recipe.

Import packages.

import marimo as mo

Use mo.ui.array to group together many UI elements into a list.

import random

# instead of random.randint, in your notebook you'd use the value of
# an upstream UI element or other Python object
array = mo.ui.array([mo.ui.text() for i in range(random.randint(1, 10))])
array

Get the value of the UI elements using array.value

array.value

Create a dictionary of UI elements#

Use cases. Same as for creating an array of UI elements, but lets you name each of the wrapped elements with a string key.

Recipe.

Import packages.

import marimo as mo

Use mo.ui.dictionary to group together many UI elements into a list.

import random

# instead of random.randint, in your notebook you'd use the value of
# an upstream UI element or other Python object
dictionary = mo.ui.dictionary({str(i): mo.ui.text() for i in range(random.randint(1, 10))})
dictionary

Get the value of the UI elements using dictionary.value

dictionary.value

Embed a dynamic number of UI elements in another output#

Use cases. When you want to embed a dynamic number of UI elements in other outputs (like tables or markdown).

Recipe.

Import packages

import marimo as mo

Group the elements with mo.ui.dictionary or mo.ui.array, then retrieve them from the container and display them elsewhere.

import random

n_items = random.randint(2, 5)

# Create a dynamic number of elements using `mo.ui.dictionary` and
# `mo.ui.array`
elements = mo.ui.dictionary(
    {
        "checkboxes": mo.ui.array([mo.ui.checkbox() for _ in range(n_items)]),
        "texts": mo.ui.array(
            [mo.ui.text(placeholder="task ...") for _ in range(n_items)]
        ),
    }
)

mo.md(
    f"""
    Here's a TODO list of {n_items} items\n\n
    """
    + "\n\n".join(
        # Iterate over the elements and embed them in markdown
        [
            f"{checkbox} {text}"
            for checkbox, text in zip(
                elements["checkboxes"], elements["texts"]
            )
        ]
    )
)

Get the value of the elements

elements.value

Create a hstack (or vstack) of UI elements with `on_change` handlers#

Use cases. Arrange a dynamic number of UI elements in a hstack or vstack, for example some number of buttons, and execute some side-effect when an element is interacted with, e.g. when a button is clicked.

Recipe.

Import packages

import marimo as mo

Create buttons in mo.ui.array and pass them to hstack – a regular Python list won’t work. Make sure to assign the array to a global variable.

import random


# Create a state object that will store the index of the
# clicked button
get_state, set_state = mo.state(None)

# Create an mo.ui.array of buttons - a regular Python list won't work.
buttons = mo.ui.array(
    [
        mo.ui.button(
            label="button " + str(i), on_change=lambda v, i=i: set_state(i)
        )
        for i in range(random.randint(2, 5))
    ]
)

mo.hstack(buttons)

Get the state value

get_state()

Create a table column of buttons with `on_change` handlers#

Use cases. Arrange a dynamic number of UI elements in a column of a table, and execute some side-effect when an element is interacted with, e.g. when a button is clicked.

Recipe.

Import packages

import marimo as mo

Create buttons in mo.ui.array and pass them to mo.ui.table. Make sure to assign the table and array to global variables

import random


# Create a state object that will store the index of the
# clicked button
get_state, set_state = mo.state(None)

# Create an mo.ui.array of buttons - a regular Python list won't work.
buttons = mo.ui.array(
    [
        mo.ui.button(
            label="button " + str(i), on_change=lambda v, i=i: set_state(i)
        )
        for i in range(random.randint(2, 5))
    ]
)

mo.hstack(buttons)

Get the state value

get_state()

Create a form with multiple UI elements#

Use cases. Combine multiple UI elements into a form so that submission of the form sends all its elements to Python.

Recipe.

Import packages.

import marimo as mo

Use mo.ui.form and Html.batch to create a form with multiple elements.

form = mo.md(
   r"""
   Choose your algorithm parameters:

   - $\epsilon$: {epsilon}
   - $\delta$: {delta}
   """
).batch(epsilon=mo.ui.slider(0.1, 1, step=0.1), delta=mo.ui.number(1, 10)).form()
form

Get the submitted form value.

form.value

Working with buttons#

Create a counter button#

Use cases. A counter button, i.e. a button that counts the number of times it has been clicked, is a helpful building block for reacting to button clicks (see other recipes in this section).

Recipe.

Import packages

import marimo as mo

Use mo.ui.button and its on_click argument to create a counter button.

# Initialize the button value to 0, increment it on every click
button = mo.ui.button(value=0, on_click=lambda count: count + 1)
button

Get the button value

button.value

Create a toggle button#

Use cases. Toggle between two states using a button with a button that toggles between True and False. (Tip: you can also just use mo.ui.switch.)

Recipe.

Import packages

import marimo as mo

Use mo.ui.button and its on_click argument to create a toggle button.

# Initialize the button value to False, flip its value on every click.
button = mo.ui.button(value=False, on_click=lambda value: not value)
button

Toggle between two outputs using the button value.

mo.md("True!") if button.value else mo.md("False!")

Re-run a cell when a button is pressed#

Use cases. For example, you have a cell showing a random sample of data, and you want to resample on button press.

Recipe.

Import packages

import marimo as mo

Create a button without a value, to function as a trigger.

button = mo.ui.button()
button

Reference the button in another cell.

# the button acts as a trigger: every time it is clicked, this cell is run
button

# Replace with your custom lgic
import random
random.randint(0, 100)

Run a cell when a button is pressed, but not before#

Use cases. Wait for confirmation before executing downstream cells (similar to a form).

Recipe.

Import packages

import marimo as mo

Create a counter button.

button = mo.ui.button(value=0, on_click=lambda count: count + 1)
button

Only execute when the count is greater than 0.

# Don't run this cell if the button hasn't been clicked, using mo.stop.
# Alternatively, use an if expression.
mo.stop(button.value == 0)

mo.md(f"The button was clicked {button.value} times")

Reveal an output when a button is pressed#

Use cases. Incrementally reveal a user interface.

Recipe.

Import packages

import marimo as mo

Create a counter button.

button = mo.ui.button(value=0, on_click=lambda count: count + 1)
button

Show an output after the button is clicked.

mo.md("#" + "🍃" * button.value) if button.value > 0 else None

Caching#

Cache expensive computations#

Use case. Because marimo runs cells automatically as code and UI elements change, it can be helpful to cache expensive intermediate computations. For example, perhaps your notebook computes t-SNE, UMAP, or PyMDE embeddings, and exposes their parameters as UI elements. Caching the embeddings for different configurations of the elements would greatly speed up your notebook.

Recipe.

Use functools to cache function outputs given inputs.

import functools

@functools.cache
def compute_predictions(problem_parameters):
   # replace with your own function/parameters
	...

Whenever compute_predictions is called with a value of problem_parameters it has not seen, it will compute the predictions and store them in a cache. The next time it is called with the same parameters, instead of recomputing the predictions, it will return the previously computed value from the cache.

See our best practices guide to learn more.

Recipes#

Control Flow#

Show an output conditionally#

Run a cell on a timer#

Require form submission before sending UI value#

Stop execution of a cell and its descendants#

Grouping UI elements together#

Create an array of UI elements#

Create a dictionary of UI elements#

Embed a dynamic number of UI elements in another output#

Create a hstack (or vstack) of UI elements with on_change handlers#

Create a table column of buttons with on_change handlers#

Create a form with multiple UI elements#

Working with buttons#

Create a counter button#

Create a toggle button#

Re-run a cell when a button is pressed#

Run a cell when a button is pressed, but not before#

Reveal an output when a button is pressed#

Caching#

Cache expensive computations#

Create a hstack (or vstack) of UI elements with `on_change` handlers#

Create a table column of buttons with `on_change` handlers#