New Component: st-theme, it returns the active theme of the Streamlit app

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Streamlit Theme

A component that returns the active theme of the Streamlit app.

Installation

pip install st-theme

Usage

The function immediately returns the active theme, when it is called. If the user manually changes the theme, after the web app is already running, it updates the returned value.

The st_theme command must only be set once in the script.

Parameters

adjust : bool, default=True

If set to True, which is the default, it makes a CSS adjustment and removes a space that would otherwise be added to the page by calling the st_theme function.

Streamlit components are meant to render something in the web app, and Streamlit adds a space for them even when there is nothing to render. Since st_theme does not render anything, and only communicates with the frontend to fetch the active theme, it makes a CSS adjustment to remove this space.

In most cases, the CSS adjustment does not interfere with the rest of the web app, however there could be some situations where this occurs. If this happens, or it is desired to disable it, pass False to adjust and, when necessary, make your own CSS adjustment with st.markdown.

Returns

theme : dict of str: str or None
A dictionary with the style settings being used by the active theme of the Streamlit app, or None, if for some reason it could not be fetched.

Notes

There is a known bug, that depends on the browser, where the theme is not returned immediately when the function is called. But it is returned normally when the user changes it.

This can be a problem in determining the initial theme of the web app. Because, by default, Streamlit uses the user’s operating system setting (which might be unknown) to automatically apply the light or dark mode to the app, when it is first rendered.

To solve the issue, it is recommended to set a default theme configuration for the app, and use its value in case of st_theme returning None.

Examples

A basic example:

import streamlit as st
from streamlit_theme import st_theme
theme = st_theme()
st.write(theme)

Example 1
[App] [Source]

An example showing the CSS adjustment made, when set to True:

import streamlit as st
from streamlit_theme import st_theme

adjust = st.toggle("Make the CSS adjustment")

st.write("Input:")
st.code(
    f"""
    st.write("Lorem ipsum")
    st_theme(adjust={adjust})
    st.write("Lorem ipsum")
    """
)

st.write("Output:")
st.write("Lorem ipsum")
st_theme(adjust=adjust)
st.write("Lorem ipsum")

Example 2
[App] [Source]

Requirements

To use this Streamlit component in your app, you will need:

  • Python 3.8+
  • Streamlit 1.29+
    • Older versions of Streamlit will still return the active theme, as long as the version supports sending the theme object to the component. What will not work though is the CSS adjustment. In this case, set adjust to False. The correct adjustment also depends on browser compatibility for the :has pseudo-class.

GitHub Repository

The information provided here is subject to change. For the most up-to-date documentation, visit the repository on GitHub.

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