Streamlit dynamic UI to generate dynamic input widgets depending on value from a different input widget

Question

I want to open this post as I can't find anything on the official documentation from streamlit or any resources that mentioned how to do this. After some trial and error I have figured out a way, and will post the answer below. This is a function that in R shiny is called dynamic UI, here's the question.

How to generate dynamic input widgets depending on the value from a different input widget? For example see below picture, the numbers of text_input called Product Code i depends on the value from the number_input called Number of Products. So if there are x number of products, there will be x number of text_input generated dynamically. Moreover, the value inside the generated text_input can be extracted as well.

Answer 1

Here is one way to do this.
First, use list comprehension to store keys (variables to use to extract values from text_input later) and values (text_input).
Next, use key and value to set the attribute in a class.
The value from text_input labelled as product2 can be extracted using the attribute within the class using p.product2 for example.

import streamlit as st

number_of_products = st.sidebar.number_input(label="Number of Products",
                                     min_value=0, max_value=20, value=1)

class Products:
    pass

p = Products()
keys = [str("product"+str(x+1)) for x in range(number_of_products)]
values = [st.sidebar.text_input(label=f"Product Code {x+1}", value=0) for x in range(number_of_products)]

for key, value in zip(keys, values):
    setattr(p, key, value)

# each key's value is stored in the class as an attribute
st.write(p.product2)

Using dictionary and exec command can also dynamically declare variables, but when the value inside the text_input is not a number, it will generate an error.