Top 50 Streamlit Interview Questions and Answers

What is Streamlit?
Streamlit is an open-source Python framework for building interactive and data-driven web applications easily.
How does Streamlit differ from traditional web frameworks like Flask or Django?
- Streamlit is focused on data visualization and app creation with minimal coding.
- No need to define HTML, CSS, or JavaScript for the UI.
How do you install Streamlit?
bash
pip install streamlit
How do you run a Streamlit app?
Use the command:
bash
streamlit run app.py
What are Streamlit widgets?
Widgets in Streamlit allow users to interact with apps. Examples include sliders, buttons, and text inputs.
What is the st.write() function used for?
The st.write() function is a versatile method to display text, data, or visualizations in a Streamlit app.
Can Streamlit handle real-time data updates?
Yes, Streamlit can update data in real-time using st.experimental_rerun() or st.cache_data to optimize performance.
What is the st.sidebar used for?
The st.sidebar creates a side panel for widgets and inputs, improving the app’s organization.
What kind of data visualizations can you create with Streamlit?
Streamlit supports visualizations using libraries like Matplotlib, Seaborn, Plotly, and Altair.
How do you upload a file in Streamlit?
Use st.file_uploader() to allow users to upload files in the app.

How do you create a slider in Streamlit?
python
slider_value = st.slider("Choose a value", 0, 100)
What is the use of st.cache_data?
It is used to cache expensive computations and prevent re-execution on every rerun.
How do you display an image in Streamlit?
Use st.image() with the image file path or a PIL image object.
How can you create a multi-page Streamlit app?
Use the Streamlit App Template feature or custom routing logic with buttons and conditionals.
How do you create a dropdown in Streamlit?
python
option = st.selectbox("Choose an option", ["Option 1", "Option 2"])
What is st.pyplot() used for?
Displays Matplotlib plots directly in the app.
How do you display a table in Streamlit?
Use st.table() or st.dataframe().
How can you integrate a Plotly chart into Streamlit?
python
import plotly.express as px fig = px.scatter(...) st.plotly_chart(fig)
How do you add a checkbox in Streamlit?
python
checkbox = st.checkbox("Check me!")
What is the difference between st.table() and st.dataframe()?
- st.table(): Displays a static table.
- st.dataframe(): Displays an interactive table.

How do you deploy a Streamlit app?
Streamlit apps can be deployed on platforms like Streamlit Community Cloud, Heroku, or AWS.
How do you make Streamlit apps reactive?
Streamlit automatically reruns the script when widget states change, making it inherently reactive.
What is the purpose of st.multiselect()?
Allows users to select multiple options from a list.
How do you handle session state in Streamlit?
Use st.session_state to store and persist data across reruns.
Can Streamlit integrate with APIs?
Yes, you can use Python libraries like requests to fetch and display API data.
What is the role of st.progress()?
Displays a progress bar in the app.
How do you create radio buttons in Streamlit?
python
choice = st.radio("Select an option", ["A", "B", "C"])
What is st.metric() used for?
Displays a numeric value with an optional delta indicator for comparisons.
How do you use markdown in Streamlit?
Use st.markdown() to display formatted text using Markdown syntax.
Can you embed HTML in a Streamlit app?
Yes, but with limited support using st.markdown(unsafe_allow_html=True).

How would you implement real-time data updates in Streamlit?
Use st.experimental_rerun() or a while loop with time.sleep().
How do you display multiple charts side by side?
Use the st.columns() layout:
python
col1, col2 = st.columns(2) col1.write("Chart 1") col2.write("Chart 2")
How do you secure sensitive credentials in a Streamlit app?
Store them in environment variables or use secret management tools.
How do you capture user inputs from multiple widgets?
Combine inputs from widgets like sliders, text inputs, and checkboxes using conditional logic.
How can you export data from Streamlit?
Use st.download_button() for users to download data files.

How do you debug a Streamlit app?
Use Python debugging tools like pdb or add st.write() statements for insights.
What are common performance issues in Streamlit?
- Inefficient data processing.
- Overuse of re-executing functions.
How do you optimize a Streamlit app?
- Use st.cache_data for caching.
- Minimize redundant computations.
How do you test a Streamlit app?
Use Python testing frameworks like pytest for unit testing the underlying logic.
How do you monitor a deployed Streamlit app?
Use platform-specific monitoring tools or log analysis.

What is the purpose of st.container()?
Groups widgets and outputs together for better layout control.
How do you customize the Streamlit app theme?
Modify the config.toml file to set light or dark themes.
What are some alternatives to Streamlit?
- Dash (by Plotly)
- Flask combined with visualization libraries
How do you handle multilingual support in Streamlit?
Use libraries like gettext or create language-based dictionaries.
What are the limitations of Streamlit?
- Not ideal for complex UI requirements.
- Limited scalability without external tools.