Fix Streamlit Plotly Chart Deprecation Warning

So, you're building a slick data visualization with Streamlit and using st.plotly_chart, which is fantastic! It's a powerful way to embed interactive Plotly graphs directly into your web apps. You're aiming for that perfect layout, perhaps setting the width='content' to make your chart smartly adapt to its container. And then, bam, you hit a deprecation warning. It pops up, mentioning something about kwargs and how they're being phased out. This can be a bit confusing, especially when you feel like you're just using the documented parameters and not any sneaky, extra keyword arguments. Let's dive into what's happening, why it's happening, and most importantly, how to smoothly navigate it.

Understanding the plotly_chart Kwargs Deprecation Warning

At its core, this issue revolves around how Streamlit handles arguments passed to st.plotly_chart, specifically when you're trying to control the chart's dimensions using parameters like width='content' or height='content'. The warning message: "Variable keyword arguments for st.plotly_chart have been deprecated and will be removed in a future release. Use the config argument instead to specify Plotly configuration options," suggests that Streamlit is interpreting these dimension arguments as kwargs that are being deprecated. This is happening even when you're not explicitly passing any unintended keyword arguments. The expectation, and the current behavior in older versions, is that using documented parameters like width should not trigger such a warning. This warning is essentially a heads-up that the way certain arguments are being processed is changing, and you should adapt to the new method to avoid issues in future updates.

Why is This Happening?

This warning typically arises from changes in Streamlit's internal handling of arguments passed to its components. Libraries, including Streamlit, evolve over time. Developers often refactor code to improve efficiency, maintainability, or to align with new best practices. In this case, it appears that Streamlit's developers have decided to centralize certain configuration options, including layout-related ones that affect the chart's display, within a dedicated config argument. Previously, parameters like width might have been handled more directly or perhaps through a broader **kwargs mechanism. Now, the intention is to funnel these through a structured config dictionary. This makes the API cleaner and more predictable. The warning is triggered because the width and height parameters, when set to values like 'content', are being caught by a check designed to identify and warn about the use of deprecated kwargs. It's a bit like a security guard seeing someone walk through a door that's supposed to be for authorized personnel only, even if the person has a valid reason to be there. The system is flagging it based on a rule that's being updated.

The Impact on Developers

For developers, this deprecation warning, while informative, can be a minor annoyance. It doesn't necessarily break your application right now, but it signifies that the current approach might not be supported indefinitely. Ignoring deprecation warnings is generally not a good long-term strategy, as the functionality they point to will eventually be removed, potentially causing your application to malfunction when you update Streamlit. The immediate impact is seeing that warning in your console or Streamlit's UI, which can clutter your development output. More significantly, it signals a need to update your code to align with Streamlit's evolving API, ensuring your application remains robust and compatible with future versions.

Reproducing the Issue: A Code Example

To truly understand a problem, it's best to see it in action. The provided code example clearly demonstrates how to trigger this warning. It's a straightforward setup using Streamlit and Plotly:

import plotly.graph_objects as go
import streamlit as st

fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
fig.update_layout(width=500, height=360)

st.plotly_chart(fig, width="content")

Step-by-Step Reproduction

1. Import Libraries: Start by importing plotly.graph_objects as go and streamlit as st.
2. Create a Plotly Figure: Instantiate a go.Figure() object. Add a trace to it, for instance, a go.Barpolar trace, to give it some substance. You can use sample data as shown.
3. Update Layout: Set some initial layout dimensions for the figure using fig.update_layout(width=500, height=360). This step isn't strictly necessary to trigger the warning but is good practice for defining your base plot.
4. Display with st.plotly_chart: This is the key step. Call st.plotly_chart(fig, width="content"). The width="content" argument is what seems to be triggering the deprecation warning.

When you run this code in your Streamlit application, you'll observe the Plotly chart rendering correctly, but alongside it, the deprecation warning related to kwargs will appear. This confirms that the issue is reproducible with this specific usage pattern.

The Expected vs. Current Behavior

It's crucial to understand the discrepancy between what you anticipate and what's actually happening. The intended behavior and the expected outcome are quite clear, while the current behavior highlights the bug or change that needs addressing.

Expected Behavior

When Streamlit introduced changes to handle kwargs more granularly, and specifically encouraged the use of a config argument for Plotly options, the expectation was that documented parameters like width and height should continue to function as before without triggering deprecation warnings. If you pass width='content' or height='content' to st.plotly_chart, the chart should render with its width adjusting to the container, and no deprecation warning should be shown. This implies that these specific, well-defined parameters should be recognized and handled appropriately, distinct from general, arbitrary keyword arguments.

Current Behavior

However, the current behavior, as reported and demonstrated in the reproducible code, is that using width='content' (or height='content') does trigger the kwargs deprecation warning. This occurs because Streamlit's internal logic, particularly the check if kwargs:, is catching these parameters as if they were general keyword arguments being passed in a deprecated manner. The warning message, "Variable keyword arguments for st.plotly_chart have been deprecated and will be removed in a future version. Use the config argument instead to specify Plotly configuration options," is displayed. This indicates a mismatch between how Streamlit is interpreting the width and height arguments and how they are intended to be used according to the documentation.

Addressing the Warning: Moving to config

The warning message itself provides a clear directive: "Use the config argument instead to specify Plotly configuration options." This is the recommended way forward to ensure your Streamlit applications remain compatible and avoid issues in the future. Let's see how to implement this.

The config Argument Explained

In Streamlit's st.plotly_chart function, the config argument is a dictionary where you can pass Plotly.js configuration options. This is a more structured and explicit way to control various aspects of your Plotly chart's display and interactivity, including dimensions. Instead of passing width or height directly to st.plotly_chart, you'll embed these (or related settings) within the config dictionary.

How to Modify the Code

To resolve the deprecation warning and adopt the recommended practice, you need to restructure your st.plotly_chart call. Instead of:

st.plotly_chart(fig, width="content")

You should use the config argument like this:

st.plotly_chart(fig, config={"responsive": True, "autosize": True})

Wait, what happened to width='content'? That's a great question! The Plotly.js config object doesn't directly have a width or height parameter in the same way Streamlit's st.plotly_chart used to. Instead, it relies on properties like "responsive": True and "autosize": True. When you set responsive to True, Plotly is instructed to automatically adjust the chart's size to fit its container. This effectively achieves the same outcome as width='content' in many scenarios. autosize: True complements this by ensuring the chart's layout itself is also responsive.

Important Note: While width='content' was a convenient Streamlit-specific parameter, the underlying Plotly.js library handles responsiveness differently. By using config={"responsive": True, "autosize": True}, you're leveraging Plotly's own mechanisms for responsive sizing, which is the intended path forward as per Streamlit's evolution.

Benefits of Using config

Adopting the config argument offers several advantages:

• Future-Proofing: Your code will be compatible with future versions of Streamlit, as the deprecated kwargs handling is removed.
• Clarity and Structure: The config dictionary provides a centralized and organized place for all Plotly-related configurations, making your code easier to read and manage.
• Access to More Features: The config object in Plotly.js offers a wide range of options for controlling chart behavior, interactivity, and appearance that go beyond simple dimensions.
• Consistency: It aligns with how other libraries or components might handle complex configurations, promoting a more standardized approach.

Is This a Regression?

Yes, the issue is indeed considered a regression. A regression in software development occurs when a change introduces a bug or causes previously working functionality to stop working as expected. In this case, the ability to use st.plotly_chart with dimension parameters like width='content' without encountering a deprecation warning worked in previous versions of Streamlit. The introduction of the kwargs warning mechanism has inadvertently broken this expected behavior, hence classifying it as a regression.

Debugging Information

To help pinpoint issues and track down bugs, it's always useful to have detailed debugging information. Here's a breakdown of the environment where this issue was observed:

• Streamlit Version: 1.50.0 - This is the specific version where the warning is present.
• Python Version: 3.14.2 - The Python interpreter version used.
• Operating System: MacOs 26.1 - The OS environment.
• Browser: Chrome - The web browser used to view the Streamlit app.

This information is vital for developers to replicate the environment and test potential fixes. It helps ensure that the solution is effective across similar setups.

Conclusion: Embracing the Change

While the plotly_chart kwargs deprecation warning might seem like a small hiccup, it's a clear signal from the Streamlit development team about the evolving API. The move towards a more structured config argument for Plotly configurations, including responsive sizing, is a positive step for maintainability and clarity. By understanding the cause of the warning and adopting the recommended config={"responsive": True, "autosize": True} approach, you not only eliminate the warning but also future-proof your Streamlit applications. This change ensures your interactive charts display beautifully and adapt seamlessly to your users' screens, keeping your data storytelling engaging and effective.

For more in-depth information on Plotly configurations and how to best utilize them within Streamlit, I highly recommend checking out the official documentation:

• Streamlit Documentation on Displaying Plots: You can find comprehensive guides and examples on integrating various plotting libraries, including Plotly, into your Streamlit apps. This resource is invaluable for understanding best practices and advanced features. Visit Streamlit Docs.
• Plotly.js Configuration Options: For a deep dive into the config object and its extensive capabilities for customizing Plotly charts, refer to the official Plotly.js documentation. This will give you the full picture of what's possible with chart configuration. Check out Plotly.js Configuration Documentation.