Streamlit Download Button: A Comprehensive Guide

Adding a download button to your Streamlit app enhances user experience by allowing them to easily save generated files, reports, or data visualizations. This guide covers everything you need to know about implementing a Streamlit Download Button, from basic examples to advanced techniques.

Simple File Downloads with Streamlit

Let’s start with the simplest scenario: downloading a pre-existing file. This can be achieved using the st.download_button. You simply provide the file path, a descriptive label for the button, and optionally, the desired filename for the downloaded file.

import streamlit as st

with open("my_file.txt", "r") as f:
    file_contents = f.read()

st.download_button("Download Text File", file_contents, file_name="downloaded_file.txt")

This straightforward approach works well for static files. But what about dynamically generated content?

Downloading Dynamically Generated Content

Streamlit’s versatility shines when handling dynamic content. Whether you’re creating dataframes, plots, or any other data, you can provide the download button with the content directly.

import streamlit as st
import pandas as pd

df = pd.DataFrame({"col1": [1, 2, 3], "col2": [4, 5, 6]})

csv = df.to_csv(index=False).encode('utf-8')

st.download_button("Download CSV", csv, "data.csv", "text/csv")

Streamlit Download Button Dynamic CSV Download

Notice how the to_csv method converts the DataFrame to a CSV string, which is then passed to the st.download_button. The mime argument is crucial for specifying the correct file type, ensuring proper handling by the browser.

Advanced Techniques and Considerations

Streamlit’s st.download_button offers flexibility for various use cases. You can download different file types, like images or PDFs, by adjusting the mime argument accordingly. For larger files, consider using techniques to optimize download speed and minimize browser impact.

import streamlit as st
from io import BytesIO
from PIL import Image

image = Image.new('RGB', (200, 100))

img_bytes = BytesIO()
image.save(img_bytes, format='PNG')

st.download_button('Download Image', img_bytes.getvalue(), 'image.png', 'image/png')

What if you need to offer multiple download options? You can easily create separate download buttons for different files or data formats, catering to diverse user needs.

Handling Different File Types

Streamlit allows you to download a variety of file types. By specifying the correct MIME type, you ensure that the browser interprets the downloaded data correctly.

Conclusion

The streamlit download button provides a powerful and user-friendly way to enhance your Streamlit applications. From downloading static files to dynamically generated content, this feature simplifies the process of sharing data and results with your users. By following the examples and tips in this guide, you can effectively integrate download functionality into your Streamlit apps.

FAQ

How do I download a CSV file in Streamlit? Use st.download_button with the to_csv method of a Pandas DataFrame.
Can I download images using Streamlit? Yes, use st.download_button with the correct MIME type for images (e.g., ‘image/png’).
How can I download large files efficiently? Consider using techniques like file compression or streaming to optimize download speed.
Is it possible to download multiple files at once? While not directly, you can create separate download buttons for each file.
What is the mime argument in st.download_button? It specifies the file type, allowing the browser to handle the download correctly.
How can I customize the filename of the downloaded file? Use the file_name argument in st.download_button.
Can I download data generated by a Streamlit component? Yes, capture the output of the component and pass it to st.download_button.

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