import streamlit as st

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

d1 = fetch_and_clean_data(DATA_URL_1)
# Actually executes the function, since this is the first time it was
# encountered.

d2 = fetch_and_clean_data(DATA_URL_1)
# Does not execute the function. Instead, returns its previously computed
# value. This means that now the data in d1 is the same as in d2.

d3 = fetch_and_clean_data(DATA_URL_2)
# This is a different URL, so the function executes.

要设置persist参数，请按如下方式使用此命令：

import streamlit as st

@st.cache_data(persist="disk")
def fetch_and_clean_data(url):
    # Fetch data from URL here, and then clean it up.
    return data

默认情况下，缓存函数的所有参数都必须是可哈希的。 任何以_开头的参数将不会被哈希。你可以使用 这个作为不可哈希参数的“逃生舱口”：

import streamlit as st

@st.cache_data
def fetch_and_clean_data(_db_connection, num_rows):
    # Fetch data from _db_connection here, and then clean it up.
    return data

connection = make_database_connection()
d1 = fetch_and_clean_data(connection, num_rows=10)
# Actually executes the function, since this is the first time it was
# encountered.

another_connection = make_database_connection()
d2 = fetch_and_clean_data(another_connection, num_rows=10)
# Does not execute the function. Instead, returns its previously computed
# value - even though the _database_connection parameter was different
# in both calls.

可以程序化地清除缓存函数的缓存：

import streamlit as st

@st.cache_data
def fetch_and_clean_data(_db_connection, num_rows):
    # Fetch data from _db_connection here, and then clean it up.
    return data

fetch_and_clean_data.clear(_db_connection, 50)
# Clear the cached entry for the arguments provided.

fetch_and_clean_data.clear()
# Clear all cached entries for this function.

要覆盖默认的哈希行为，可以传递一个自定义的哈希函数。 你可以通过将一个类型（例如 datetime.datetime）映射到一个哈希 函数（lambda dt: dt.isoformat()）来实现，如下所示：

import streamlit as st
import datetime

@st.cache_data(hash_funcs={datetime.datetime: lambda dt: dt.isoformat()})
def convert_to_utc(dt: datetime.datetime):
    return dt.astimezone(datetime.timezone.utc)

或者，您可以将类型的完全限定名称（例如 "datetime.datetime"）映射到哈希函数：

import streamlit as st
import datetime

@st.cache_data(hash_funcs={"datetime.datetime": lambda dt: dt.isoformat()})
def convert_to_utc(dt: datetime.datetime):
    return dt.astimezone(datetime.timezone.utc)

import streamlit as st
import time

@st.cache_data
def foo(bar):
    time.sleep(2)
    st.write(f"Executed foo({bar}).")
    return bar

if st.button("Clear all cached values for `foo`", on_click=foo.clear):
    foo.clear()

if st.button("Clear the cached value of `foo(1)`"):
    foo.clear(1)

foo(1)
foo(2)