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Hello World

Display a simple “Hello, World!” message using Preswald:

from preswald import text

text("# Hello, World!")

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Data Viewer

Connect to a CSV file and display the data using Preswald’s viewer:

from preswald import connect, get_df, table

data = get_df("example_data.csv")
table(data)

Connect to a JSON file and display the data using Preswald’s viewer:

from preswald import connect, get_df, view

data = get_df("user_event.csv")
view(data)

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Interactive Dashboard

Create an interactive dashboard where users can control how many rows of data to display:

from preswald import text, slider, table

text("# Interactive Dashboard")

rows = slider("Rows to Display", min_val=5, max_val=50, default=10)
table(data, limit=rows)

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Automatic Reactivity

Preswald automatically detects dependencies between top level expressions and selectively recomputes only the parts of your script that need to update.

from preswald import slider, text

base = slider("Base", min_val=1, max_val=10, default=2)
double = base * 2
text(f"Double: {double}")

You can also include side effects like logging:

import logging
from preswald import slider

logger = logging.getLogger(__name__)

val = slider("Level", min_val=0, max_val=5, default=1)
logger.info(f"Slider moved: {val}")

Preswald will:

  • Lift each top level statement into an atom
  • Automatically track dependencies like double -> base
  • Ensure logger.info(…) runs again only when val changes

No decorators or workflow setup required, just plain Python

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Tuple Unpacking + Reactive Consumers

Preswald also supports tuple unpacking and reactive consumers:

from preswald import slider, text

def compute_pair(n):
    return (n, n * 2)

val = slider("Input", min_val=1, max_val=10, default=3)
a, b = compute_pair(val)
text(f"a: {a}, b: {b}")

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Learn More

To explore these examples in depth and discover additional use cases, check out the Preswald Examples. You’ll find comprehensive guides and example projects to help you make the most of Preswald.