1. Contents
  2. Caching
  3. Browser and server state
  4. Deprecated commands

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).

Python
@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).

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

Browser and server state

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

Context

st.context provides a read-only interface to access cookies, headers, locale, and other browser-session information.

Python
st.context.cookies
st.context.headers

Session State

Save data between reruns and across pages.

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

Query parameters

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

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

Deprecated commands

delete

Get query parameters

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

Python
param_dict = st.experimental_get_query_params()
delete

Set query parameters

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

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