How to clear screen/make blank again?

Using Streamlit
1

I want to print some text, then clear the screen, and then print some more text. Is there a command that I can use to accomplish this?

2

You can use st.empty to keep a placeholder that can be cleaned whenever you want to add new elements.

Here is a unnecessarily convoluted fun example:

emptyContainer

import streamlit as st

if "page" not in st.session_state:
    st.session_state.page = 0

def nextpage(): st.session_state.page += 1
def restart(): st.session_state.page = 0

placeholder = st.empty()
st.button("Next",on_click=nextpage,disabled=(st.session_state.page > 3))

if st.session_state.page == 0:
    # Replace the placeholder with some text:
    placeholder.text(f"Hello, this is page {st.session_state.page}")

elif st.session_state.page == 1:
    # Replace the text with a chart:
    placeholder.line_chart({"data": [1, 5, 2, 6]})

elif st.session_state.page == 2:
# Replace the chart with several elements:
    with placeholder.container():
        st.write("This is one element")
        st.write("This is another")
        st.metric("Page:", value=st.session_state.page)

elif st.session_state.page == 3:
    placeholder.markdown(r"$f(x) = \exp{\left(x^🐈\right)}$")

else:
    with placeholder:
        st.write("This is the end")
        st.button("Restart",on_click=restart)
3

This doesn’t seem to work when not triggered by a UI event. How does one clear the screen in response to some other kind of event - e.g. expiration of a timer, or a notification completion of a task coming from a remote service?

1 Like
4

You could use with st.empty():.

Example:

import streamlit as st
import time

def next_page():
    placeholder.empty()
    if(st.session_state['button1_pressed'] < 4):
        st.session_state['button1_pressed'] += 1

def previous_page():
    placeholder.empty()
    if(st.session_state['button1_pressed'] > 1):
        st.session_state['button1_pressed'] -= 1

if 'button1_pressed' not in st.session_state:
    st.session_state['button1_pressed'] = 1

placeholder = st.empty()

with st.empty():

        if(st.session_state['button1_pressed'] == 1):
            with st.container():
                st.write("This is page one")
                cols1, cols2, cols3, cols4, cols5 = st.columns([1,1,1,1,1])
                with cols1:
                    st.button('<',key='<1',on_click=previous_page)

                with cols5:
                    st.button('>',key='1>',on_click=next_page)
            time.sleep(5)
            next_page()

        if(st.session_state['button1_pressed'] == 2):
            with st.container():
                st.write("This is page two")
                cols1, cols2, cols3, cols4, cols5 = st.columns([1,1,1,1,1])
                with cols1:
                    st.button('<',key='<2',on_click=previous_page)

                with cols5:
                    st.button('>',key='2>',on_click=next_page)
            time.sleep(5)
            next_page()

        if(st.session_state['button1_pressed'] == 3):
            with st.container():
                st.write("This is page three")
                cols1, cols2, cols3, cols4, cols5 = st.columns([1,1,1,1,1])
                with cols1:
                    st.button('<',key='<3',on_click=previous_page)

                with cols5:
                    st.button('>',key='3>',on_click=next_page)
            time.sleep(5)
            next_page()

        if(st.session_state['button1_pressed'] == 4):
            with st.container():
                st.write("This is page four")
                cols1, cols2, cols3, cols4, cols5 = st.columns([1,1,1,1,1])
                with cols1:
                    st.button('<',key='<4',on_click=previous_page)

                with cols5:
                    st.button('>',key='4>',on_click=next_page)
            time.sleep(5)

change_page

5

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