Fixing Plotly Chart Deprecation Warning In Streamlit

Hey there, data visualization enthusiasts! If you've been working with Streamlit and noticed a pesky deprecation warning popping up when using st.plotly_chart, especially with parameters like width="content", you're not alone. It can be a bit confusing when you're trying to follow the documentation, only to be greeted by a warning about kwargs even when you're not explicitly using any variable keyword arguments. Let's dive into what's happening and how to navigate this.

Understanding the kwargs Warning in st.plotly_chart

The kwargs (keyword arguments) deprecation warning in Streamlit's st.plotly_chart function is primarily triggered when the function detects that you might be passing arguments that aren't explicitly defined in its signature. This can happen even if you're using documented parameters that internally might be passed along as keyword arguments to the underlying Plotly library. Essentially, Streamlit is trying to guide users towards a more structured way of passing Plotly-specific configurations, which is through the config argument, rather than relying on direct keyword arguments to st.plotly_chart that are then forwarded to Plotly. The intention behind this change is to provide a clearer separation between Streamlit's own arguments for controlling the chart's display (like width, height, use_container_width) and Plotly's extensive configuration options. When you use width="content", Streamlit interprets this as a directive to size the chart based on its container, which is a useful feature. However, the way this is handled internally might have led to the kwargs warning being raised. It's a sign that the library is evolving to enforce best practices and prevent potential conflicts or ambiguities as new features are added. The warning message itself, which suggests using the config argument, is a hint towards this more organized approach. For instance, if you wanted to set Plotly-specific options like interactivity modes or tooltips, those would ideally go into the config dictionary. The current situation suggests a slight mismatch between how width="content" is being processed and Streamlit's warning system, which flags any non-standard keyword argument passing. This can be particularly frustrating when you're following the official documentation for parameters like width and height, which are documented as valid arguments for st.plotly_chart. The goal is to ensure that when you specify a chart's dimensions or layout properties using Streamlit's interface, it's done in a way that doesn't trigger these unintended warnings. This is crucial for maintaining a clean and informative development experience. The deprecation warning is a signal to adapt to the new patterns, ensuring that your code remains robust and forward-compatible as Streamlit and Plotly continue to develop.

Why This Warning Appears and What It Means

This particular warning stems from a change Streamlit made to streamline how configurations are passed to Plotly charts. Previously, it was more permissible to pass various keyword arguments directly to st.plotly_chart, and Streamlit would try its best to pass them on to the Plotly figure. However, this could lead to confusion and potential conflicts, especially as both Streamlit and Plotly evolve their features. The introduction of the config argument in st.plotly_chart is designed to be the single, designated place for all Plotly-specific configurations. This includes things like scrollZoom, displaylogo, modeBarButtonsToRemove, and many others. When you use st.plotly_chart(fig, width="content"), you're telling Streamlit to automatically adjust the chart's width to fit its container. While this is a documented and intended use of st.plotly_chart, the internal mechanism for handling this might have been inadvertently caught by the new kwargs check. The warning isn't necessarily saying you are doing something wrong in terms of basic usage, but rather that the way Streamlit is processing your input (even valid input) is triggering a check designed to catch broader kwargs misuse. The developers introduced this check to encourage users to consolidate all Plotly configurations into the config dictionary. This makes the API cleaner and less prone to errors. For example, if you wanted to pass Plotly layout options that aren't directly exposed by st.plotly_chart's own arguments, the config dictionary is the correct place. The width="content" parameter, while a Streamlit-specific argument for controlling the chart's embedding, seems to be causing a false positive with this new warning. It's a common challenge in software development where a general rule meant to improve code quality can sometimes flag legitimate, specific use cases. The intent is to make your Streamlit applications more robust and easier to maintain by having a predictable way to manage chart properties. This warning is a gentle nudge towards that more structured approach. It's important to remember that this isn't a bug in your code, but rather an indication of an evolving API in Streamlit that aims for better clarity and control over how Plotly charts are integrated.

Reproducible Code Example and Steps

To illustrate the issue, let's look at the provided reproducible code example:

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")

When you run this code in Streamlit version 1.50.0 or similar, you'll observe the kwargs deprecation warning. The steps to reproduce are straightforward:

1. Create a Plotly Figure: Initialize a plotly.graph_objects.Figure and add some traces. In this example, a Barpolar trace is used for demonstration.
2. Update Layout (Optional but good practice): You can set initial layout properties for the figure, though st.plotly_chart will override some of these.
3. Display with st.plotly_chart: Use st.plotly_chart(fig, width="content"). The crucial part here is passing width="content". This argument tells Streamlit to make the chart responsive and fit its containing element, which is a very common and useful way to embed charts.
4. Observe the Warning: Upon running your Streamlit app, you will see the deprecation warning related to kwargs, even though you haven't explicitly passed any undefined kwargs to st.plotly_chart. The warning message typically reads something like: "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."

This behavior is considered a regression because, in previous versions, using width="content" did not trigger this specific warning. The intention was likely to ensure that all Plotly-specific options are funneled through the config parameter, but it seems the width parameter, being a Streamlit-specific control, is being incorrectly flagged.

• Debug Info:
  • Streamlit version: 1.50.0
  • Python version: 3.14.2
  • Operating System: MacOs 26.1
  • Browser: Chrome

This setup clearly shows that the issue is tied to the interaction between st.plotly_chart's handling of the width parameter and its internal kwargs deprecation check.

Expected vs. Current Behavior

Let's clarify what we expect versus what's actually happening. The core of the issue lies in how Streamlit handles chart dimensions and configurations.

Expected Behavior

When you update st.plotly_chart to use the width argument (as recommended by documentation, moving away from potentially deprecated use_container_width in some contexts), the expectation is that this documented parameter functions correctly without side effects. Specifically, using width="content" should instruct Streamlit to render the Plotly chart with a width that dynamically adapts to its parent container. This is a highly desirable feature for creating responsive web applications. Critically, this usage should not result in a deprecation warning related to kwargs. The kwargs warning is intended for situations where you might be passing arbitrary, undocumented keyword arguments that could conflict with Streamlit's internal workings or future updates. Therefore, providing a clearly defined and documented argument like width should be exempt from this warning.

Current Behavior

As reported, the current behavior is that even when using documented parameters like width="content", a deprecation warning related to kwargs is being shown. This occurs because of a specific code block introduced in recent Streamlit versions:

if kwargs:
    show_deprecation_warning(
        "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."
    )

This condition if kwargs: checks if there are any keyword arguments remaining after Streamlit has processed its own recognized arguments. When you pass width="content", Streamlit processes it, but if there are any other unhandled keyword arguments (or if the internal handling of width itself is being passed in a way that appears as an unhandled kwargs to this check), the warning is triggered. This suggests that the width parameter, while a legitimate argument for st.plotly_chart, is not being properly excluded from this kwargs check by the Streamlit core logic. This leads to the warning appearing even when the user is following best practices by using documented parameters.

Is This a Regression?

Yes, this is a regression. The issue description explicitly states, "This used to work in a previous version." This means that in earlier versions of Streamlit, you could use st.plotly_chart(fig, width="content") without encountering the kwargs deprecation warning. The warning has only started appearing after specific changes were made to how st.plotly_chart handles keyword arguments and configurations. Regressions are significant because they indicate that a previously stable and functional feature has been broken, impacting user workflows and potentially introducing confusion. The goal of software updates is generally to add features or improve existing ones, not to break established functionality. This particular regression highlights a challenge in API evolution: ensuring that new restrictions or warnings, while intended to improve code quality and future-proofing, do not negatively affect current, valid usage patterns.

Navigating the kwargs Warning

While the ideal solution is for Streamlit to address this by correctly identifying documented arguments like width and exempting them from the kwargs warning, there are a few ways you can manage this in the meantime.

1. Using the config Argument (for Plotly-specific options)

The warning explicitly suggests using the config argument. While width="content" is a Streamlit-specific control and not a Plotly configuration per se, the config dictionary is indeed the correct place for any Plotly-level settings. If you were trying to control Plotly's own features (like enabling/disabling zoom, adding custom buttons to the mode bar, etc.), you would pass them like this:

config_dict = {
    "scrollZoom": True,
    "displaylogo": False,
}
st.plotly_chart(fig, config=config_dict)

This doesn't directly solve the width="content" warning but reinforces the intended pattern for Plotly configurations.

2. Ignoring the Warning (with caution)

If the warning is purely cosmetic and doesn't affect the functionality of your chart (i.e., the chart displays correctly with the desired width), you might choose to ignore it for the time being. This is generally not recommended for long-term solutions, as warnings can sometimes precede breaking changes. However, in a pinch, if the app is otherwise stable, you might proceed. Be sure to keep an eye on Streamlit updates for a fix.

3. Pinning to an Older Version (Temporary Workaround)

As a temporary workaround, you could pin your Streamlit version to one prior to when this regression was introduced. This is not ideal for long-term development, as you'll miss out on new features and security updates. To do this, you would modify your requirements.txt file or environment.yml file to specify a known working version of Streamlit. For example:

streamlit==1.49.0  # Or another version known to not have this warning

Remember to check Streamlit's release notes or issue tracker to identify which version introduced this behavior and choose a version just before that.

4. Contributing to the Solution

If you're comfortable with Python and Streamlit's codebase, you could consider contributing a fix yourself! Check the Streamlit GitHub repository for open issues related to this warning. You might find an existing pull request or be able to submit one yourself. This is the most impactful way to address the problem and help the community.

Conclusion

The kwargs deprecation warning when using st.plotly_chart with width="content" is a known issue and a regression that Streamlit developers are likely aware of or will address soon. It highlights the ongoing effort to refine the library's API for better clarity and maintainability. While it can be a minor annoyance, understanding its cause – an overzealous kwargs check – provides context. For now, focusing on using the config argument for actual Plotly configurations remains the best practice. Keep an eye on the Streamlit GitHub repository for updates, as this is a common type of issue that gets resolved in subsequent releases.

For more in-depth information on Plotly configurations and how they integrate with Streamlit, I recommend checking out the official [Streamlit Documentation on Plotly Charts](https://docs.streamlit.io/library/api-reference/ செலle-components/st.plotly_chart) and the Plotly Python Documentation for a comprehensive understanding of the charting library itself.