st.button

st.button allows the display of a button widget.

What we're building?

A simple app that performs conditionally prints out alternative messages depending on whether the button was pressed or not.

Flow of the app:

1. By default, the app prints Goodbye
2. Upon clicking on the button, the app displays the alternative message Why hello there

Demo app

The deployed Streamlit app should look something like the one shown in the below link:

Code

Here's the code to implement the above mentioned app:

import streamlit as st

st.header('st.button')

if st.button('Say hello'):
     st.write('Why hello there')
else:
     st.write('Goodbye')

Line-by-line explanation

The very first thing to do when creating a Streamlit app is to start by importing the streamlit library as st like so:

import streamlit as st

This is followed by creating a header text for the app:

st.header('st.button')

Next, we will use conditional statements if and else for printing alternative messages.

if st.button('Say hello'):
     st.write('Why hello there')
else:
     st.write('Goodbye')

As we can see from the above code box, the st.button() function accepts the label input argument of Say hello, which is the text that the button displays.

The st.write function is used to print text messages of either Why hello there or Goodbye depending on whether the button was clicked or not, which is implemented via:

st.write('Why hello there')

and

st.write('Goodbye')

It is important to note that the above st.write statements are placed under the if and else conditions in order to perform the above mentioned process of alternative displaying of messages

Next steps

Now that you have created the Streamlit app locally, it's time to deploy it to Streamlit Cloud as will be explained soon in an upcoming challenge.

Because this is the first week of your challenge, we provide the full code (as shown in the code box above) and solution (the demo app) right inside this webpage.

Moving forward in the next challenges, it is recommended that you first try implementing the Streamlit app yourself.

Don't worry if you get stuck, you can always take a peek at the solution.

References

Read about st.button in the Streamlit API Documentation.