data/develop/api-reference/caching-and-state/_index.md

metadata

title: Caching and state
slug: /develop/api-reference/caching-and-state

Caching and state

Optimize performance and add statefulness to your app!

Caching

Streamlit provides powerful cache primitives for data and global resources. They allow your app to stay performant even when loading data from the web, manipulating large datasets, or performing expensive computations.

Cache data

Function decorator to cache functions that return data (e.g. dataframe transforms, database queries, ML inference).

@st.cache_data
def long_function(param1, param2):
  # Perform expensive computation here or
  # fetch data from the web here
  return data

Cache resource

Function decorator to cache functions that return global resources (e.g. database connections, ML models).

@st.cache_resource
def init_model():
  # Return a global resource here
  return pipeline(
    "sentiment-analysis",
    model="distilbert-base-uncased-finetuned-sst-2-english"
  )

Manage state

Streamlit re-executes your script with each user interaction. Widgets have built-in statefulness between reruns, but Session State lets you do more!

Session State

Save data between reruns and across pages.

st.session_state["foo"] = "bar"

Query parameters

Get, set, or clear the query parameters that are shown in the browser's URL bar.

st.query_params[key] = value
st.query_params.clear()

Deprecated commands

This command was deprecated in version 1.18.0. Use st.cache_data or st.cache_resource instead.

Caching

Function decorator to memoize function executions.

@st.cache(ttl=3600)
def run_long_computation(arg1, arg2):
  # Do stuff here
  return computation_output

This command was deprecated in version 1.18.0. Use st.cache_data instead.

Memo

Experimental function decorator to memoize function executions.

@st.experimental_memo
def fetch_and_clean_data(url):
  # Fetch data from URL here, and then clean it up.
  return data

This command was deprecated in version 1.18.0. Use st.cache_resource instead.

Singleton

Experimental function decorator to store singleton objects.

@st.experimental_singleton
def get_database_session(url):
  # Create a database session object that points to the URL.
  return session

Get query parameters

Get query parameters that are shown in the browser's URL bar.

param_dict = st.experimental_get_query_params()

Set query parameters

Set query parameters that are shown in the browser's URL bar.

st.experimental_set_query_params(
  {"show_all"=True, "selected"=["asia", "america"]}
)