Streamlit Plotly_chart Deprecation Warning Fix

Hey there, data visualization enthusiasts! Have you ever been happily crafting your interactive dashboards with Streamlit, only to be greeted by a mysterious plotly_chart kwargs deprecation warning? It can be a bit puzzling, especially when you're just trying to set the width or height of your Plotly charts using the documented parameters like width='content'. You might be thinking, "I'm not passing any extra keyword arguments! What's going on?" Well, you're not alone, and today, we're diving deep into this specific Streamlit behavior to shed some light on it and help you get back to building awesome apps without those pesky warnings.

The Curious Case of the kwargs Warning in st.plotly_chart

Let's get right to the heart of the matter. The plotly_chart kwargs deprecation warning pops up when you use st.plotly_chart and specify parameters like width='content' or height='content'. Normally, when you see a warning about kwargs (keyword arguments), it means you've passed some unspecified arguments that the function doesn't expect. However, in this particular scenario, the warning appears even when you are using only the documented parameters. This is where the confusion usually sets in. The Streamlit developers, in their effort to maintain a clean and future-proof API, introduced a change where any use of variable keyword arguments (**kwargs) within st.plotly_chart would trigger this deprecation warning. The intention was to encourage users to consolidate Plotly-specific configurations into the config argument, which is the more robust and intended way to pass such settings.

Why the Warning? A Deep Dive into Streamlit's API Evolution

Streamlit's core philosophy is to make web app development for data science as intuitive and Pythonic as possible. As the library evolves, it sometimes refactors its internal workings or API to improve performance, consistency, or to prepare for future features. The st.plotly_chart component, which seamlessly integrates Plotly charts into Streamlit apps, has seen its share of these updates. Previously, it might have been more lenient with how arguments were passed. However, as the library matured, a decision was made to centralize how Plotly-specific configurations are handled. The width and height parameters, when set to 'content', are essentially signals to Streamlit to dynamically adjust the chart's size based on its container. While these are valid and useful parameters, the underlying implementation might have been interpreted by the updated warning mechanism as potentially falling into the broader category of 'variable keyword arguments' that should be managed differently.

The config Argument: The Future of Plotly Customization in Streamlit

The warning message itself offers a clue: "Use the config argument instead to specify Plotly configuration options." This is the key takeaway. Instead of passing width='content' directly to st.plotly_chart, the recommended approach is to embed such configurations within the config dictionary. This config argument is designed to accept a wide range of Plotly-specific settings, providing a more organized and forward-compatible way to customize your charts. For example, if you want to control the layout, responsive behavior, or other Plotly-related options, the config dictionary is where you should place them. This change, while potentially causing a temporary warning, ultimately leads to a more structured and maintainable codebase when dealing with complex Plotly integrations.

What Does width='content' Actually Do?

Before we move on to the solution, let's quickly recap what width='content' and its counterpart height='content' do. When you set width='content', you're telling Streamlit to make the Plotly chart occupy the full available width of its parent container. This is incredibly useful for ensuring your charts are responsive and look good on different screen sizes. It's a way to avoid hardcoding pixel values and let Streamlit handle the layout responsively. The warning, therefore, isn't about the functionality being wrong, but rather about how that functionality is being invoked.

Reproducing the Warning: A Simple Code Example

To truly understand the issue, let's look at a concrete example. The following code snippet demonstrates how the plotly_chart kwargs deprecation warning can be triggered:

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 simple Streamlit script, you'll notice that even though you're only passing the fig object and the documented width='content' parameter to st.plotly_chart, the deprecation warning appears in your console or Streamlit's output. This is precisely the behavior we aim to address. It highlights a disconnect between the intended use of a documented parameter and the warning mechanism's interpretation of the underlying function calls. The warning message, as stated in the issue, indicates that "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."

The Impact of the Warning

While a deprecation warning might seem like a minor annoyance, it's important to address them. Warnings are essentially signals from the library maintainers that a certain way of doing things will be removed in the future. Ignoring them can lead to your application breaking when you update Streamlit or its dependencies. Furthermore, understanding and resolving these warnings often leads to adopting more robust and recommended coding practices, which is beneficial in the long run. In this case, the warning suggests a more structured way to handle Plotly configurations, which can simplify your code, especially as your applications grow in complexity.

Steps to Reproduce (As Reported)

The steps to reproduce this issue are straightforward:

1. Install necessary libraries: Ensure you have Streamlit and Plotly installed (pip install streamlit plotly).
2. Create a Python file: Save the code example provided above into a .py file (e.g., app.py).
3. Run the Streamlit app: Execute the file from your terminal using streamlit run app.py.
4. Observe the output: Check your terminal or the Streamlit app's output for the plotly_chart kwargs deprecation warning.

This simple reproduction clearly demonstrates that the warning is triggered by using width='content' directly, without any other explicit kwargs being passed.

The Expected vs. Current Behavior: What Should Happen?

It's crucial to understand what the correct behavior should be, and how it differs from the current situation. The Expected Behavior, as defined by the Streamlit documentation and community understanding, is that using documented parameters like width='content' or height='content' should not trigger a deprecation warning related to kwargs. These parameters are officially supported and intended for use. When they are employed, Streamlit should gracefully handle them without flagging them as potentially problematic variable keyword arguments. This implies that the internal mechanism responsible for issuing the kwargs warning should be intelligent enough to distinguish between legitimate, documented parameters and actual, arbitrary keyword arguments.

Current Behavior: The Unwanted Warning

Conversely, the Current Behavior is precisely the opposite. As observed and reported, when you pass width='content' to st.plotly_chart, the deprecation warning does appear. This occurs because of a specific code block introduced in recent versions of Streamlit:

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 code snippet checks if kwargs is non-empty. The issue arises because the way width='content' is handled internally might be causing kwargs to be populated in a way that this check incorrectly identifies it as an unexpected keyword argument, even though width itself is a documented parameter. This is likely a regression, meaning it worked as expected in a previous version of Streamlit and has been broken by a recent change.

Is This a Regression?

Yes, according to the information provided, this is indeed a regression. This indicates that in older versions of Streamlit, passing width='content' to st.plotly_chart did not result in a kwargs deprecation warning. This suggests that a recent update to Streamlit's plotly_chart component has inadvertently made its warning system too sensitive, flagging documented parameters as deprecated kwargs. Regressions are important to report and fix because they can disrupt existing workflows and degrade the user experience.

Debugging Information and Versions

To help pinpoint the cause of this regression, here's the environment information provided:

• Streamlit version: 1.50.0
• Python version: 3.14.2
• Operating System: macOS 26.1
• Browser: Chrome

These details are crucial for developers to reproduce the issue in a similar environment and to identify potential version conflicts or platform-specific bugs. Version 1.50.0 of Streamlit, combined with Python 3.14.2 on macOS, is the specific configuration where this behavior has been observed.

The Solution: Embracing the config Argument

While the warning is a bug and should ideally be fixed by Streamlit developers, there's a way to preemptively avoid it and adhere to the recommended practice: utilize the config argument.

Instead of:

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

You should use:

st.plotly_chart(fig, config={
 "responsive": True, # This is often implied by 'content' width
 "width": "container" # Or other Plotly-specific configurations
})

Important Note: While width='content' is a Streamlit-specific parameter for controlling chart width, Plotly's config argument primarily deals with Plotly's own configuration options. For achieving a similar effect to width='content', you might need to rely on Plotly's responsive setting within the config and potentially set the width within fig.update_layout() to a value that makes sense in context, or let the container handle it. However, the intent of the warning is to push all Plotly-related configurations, including layout aspects, into the config dictionary. The exact mapping for responsive sizing might evolve, but the principle remains: avoid passing width or height directly to st.plotly_chart if you want to silence this warning and use the newer API structure.

Revised approach based on common practices: A more direct way to handle responsive width using Plotly's configuration is often by leveraging the layout object itself or ensuring the chart is set to be responsive, which Streamlit often handles by default when not explicitly overridden.

Let's refine the example to better align with the spirit of using config for Plotly settings:

import plotly.graph_objects as go
import streamlit as st

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

# Configure Plotly figure layout
fig.update_layout(
 width=None, # Let Streamlit handle container width
 height=360,
 margin=dict(l=20, r=20, t=40, b=20)
)

# Pass Plotly configurations via the config argument
# 'responsive': True often helps charts adapt to container width
st.plotly_chart(fig, config={
 "responsive": True,
 "displaylogo": False # Example of another Plotly config option
})

In this revised example, we remove the width='content' from st.plotly_chart and instead use the config dictionary to pass Plotly-specific settings like responsive: True. We also set fig.update_layout(width=None) to indicate that the figure's width should be determined by its container, which Streamlit then manages. This approach aligns with the warning's suggestion and avoids the kwargs deprecation notice.

Conclusion: Embracing Streamlit's Evolution for Better Development

Deprecation warnings, while sometimes inconvenient, are a vital part of software development. They guide us toward more stable, efficient, and future-proof practices. The plotly_chart kwargs deprecation warning in Streamlit, though seemingly triggered by documented parameters, is a nudge to adopt a more structured approach to Plotly chart configuration using the config argument. By migrating parameters like width='content' and other Plotly-specific settings into the config dictionary, you not only silence the warning but also ensure your Streamlit applications are built using the latest recommended patterns. This leads to more maintainable code and better compatibility with future Streamlit updates. Remember, staying updated with these best practices empowers you to build more robust and sophisticated data visualizations.

For more detailed information on Streamlit's components and their recommended usage, I highly recommend checking out the official Streamlit Documentation. Additionally, for in-depth Plotly configuration options, the Plotly Python Documentation is an invaluable resource.