Fix Plotly_chart Width=content Deprecation Warning

Have you ever been happily coding along in Streamlit, building a fantastic interactive dashboard, only to be interrupted by a cryptic deprecation warning? Specifically, the one mentioning "kwargs" when you're just trying to get your Plotly charts to look just right? If you've encountered this with st.plotly_chart and tried to use width="content" (or height), you're not alone. It seems like even when you're not explicitly passing any variable keyword arguments, Streamlit is flagging something. Let's dive into what's happening and why this might be causing a bit of a head-scratcher for developers.

Understanding the "kwargs" Warning in Streamlit

The core of the issue lies in how Streamlit handles arguments passed to its components, particularly st.plotly_chart. When you use st.plotly_chart(fig, width="content"), you're telling Streamlit to automatically adjust the width of your Plotly chart to fit the content it displays. This is a super handy feature, as it helps maintain a clean and responsive layout without you having to manually specify pixel values. However, recent changes in Streamlit's internal workings, particularly around how it manages variable keyword arguments (often denoted as **kwargs in Python), have led to this warning appearing unexpectedly. 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.", is designed to guide users towards a more robust way of passing configurations. The intent is to consolidate Plotly-specific settings within the config parameter, which is a more structured approach. The problem arises because, in some scenarios, Streamlit's internal logic might interpret the use of arguments like width or height as if kwargs were being used, even when they are documented and intended parameters for st.plotly_chart itself. This can feel like a bug, especially when you're following the documentation and still getting a warning about something you aren't explicitly doing. It's a classic case of internal implementation details bleeding into the user experience, causing confusion and potentially making developers wary of using otherwise useful features.

Why width="content" Triggers the Warning

Let's zoom in on width="content". This specific argument is a directive to Streamlit to dynamically size the Plotly chart. Internally, Streamlit's plotly_chart function likely accepts a broad range of arguments, and it uses **kwargs to capture any arguments it doesn't explicitly define. When you pass width="content", it's possible that this argument is being caught by the **kwargs mechanism before being processed or passed down to the underlying Plotly library. Even though width and height are documented parameters for st.plotly_chart, the warning is triggered because the way Streamlit's code is structured might see these arguments being passed through the kwargs channel. The deprecation warning is a safeguard against developers passing arbitrary, undocumented kwargs that could break the component's functionality or security. However, in this instance, it's incorrectly flagging a documented and intended use case. This is particularly frustrating because the goal of features like width="content" is to simplify development, not add complexity or confusing warnings. The Streamlit team is actively working on refining how these arguments are handled to ensure that documented parameters don't trigger these warnings. It's a delicate balance between providing flexibility and maintaining a clean, predictable API. Until a fix is fully deployed, developers might see this warning as a minor annoyance, but it's important to understand that it's likely a side effect of Streamlit's ongoing efforts to improve its argument handling and deprecate less robust patterns.

Reproducing the Issue: A Simple Code Example

To really nail down this problem, let's look at a reproducible code example. This is crucial for anyone trying to debug or report an issue, as it provides a clear starting point. The provided example uses streamlit and plotly.graph_objects to create a simple barpolar chart. Here's the code snippet:

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 within a Streamlit application (version 1.50.0 or similar, with Python 3.14.2 on macOS, for instance), you'll likely see the deprecation warning pop up, even though you're not explicitly passing any unusual kwargs. The width="content" is the key argument here that seems to be causing the issue. The chart itself will likely render correctly, but the warning message in the console or Streamlit's output can be distracting. It suggests that the underlying mechanism for handling the width parameter, which is meant to be a user-friendly way to control chart dimensions, is inadvertently being caught by the warning system designed to flag the misuse of **kwargs. This highlights a small but significant friction point in the developer experience. The Streamlit team is aware of such issues and is continuously working to refine these internal processes. Understanding how to reproduce the bug is the first step towards a solution, and this clear example makes it easy for anyone to verify the behavior and contribute to finding a fix.

Expected vs. Current Behavior: What Should Happen?

Let's clarify the expected behavior versus what's actually happening. Ideally, when you use st.plotly_chart with documented parameters like width="content", you should not receive any deprecation warnings related to kwargs. The documentation for Streamlit and Plotly clearly indicates that arguments controlling the display dimensions are supported. Therefore, passing width="content" should simply make your chart responsive without any red flags. The warning would only be appropriate if you were passing truly variable and undocumented keyword arguments that could interfere with the component's functionality or future updates. The current behavior, however, is that this specific usage does trigger the kwargs deprecation warning. This is seen as a regression because, in previous versions of Streamlit, this functionality likely worked without generating such a warning. This implies that a recent change, possibly related to how Streamlit processes arguments or integrates with Plotly's configuration system, has introduced this unintended side effect. The goal is to ensure that the st.plotly_chart function is intuitive and that developers can confidently use its documented features without being bothered by warnings that don't apply to their specific use case. Fixing this regression means Streamlit can continue to offer seamless integration with Plotly, allowing users to focus on building great data visualizations rather than troubleshooting warnings.

The Path Forward: What's Being Done?

It's reassuring to know that issues like this kwargs deprecation warning are actively being addressed by the Streamlit development team. The fact that this is considered a regression means it's being prioritized. The warning itself is a symptom of Streamlit's ongoing effort to modernize its API and provide clearer, more robust ways for users to pass configurations. The introduction of the config argument is a move in this direction, aiming to centralize all Plotly-specific settings that go beyond basic Streamlit integration. For arguments like width and height in st.plotly_chart, the ideal scenario is that they are handled directly by Streamlit's component logic, not inadvertently falling into the kwargs bucket that triggers the deprecation notice. Developers are continuously working to refine the internal argument parsing to distinguish between documented, intended parameters and truly arbitrary kwargs. This involves careful examination of the st.plotly_chart function's codebase and how it interacts with Plotly's own configuration system. While a fix might involve a minor adjustment to the argument handling logic, the impact for users is significant – it means a cleaner, less noisy development experience. Until the patch is officially released, the community often finds workarounds, but the ultimate goal is for the core functionality to work as expected without warnings. You can often find the latest updates and discussions on these issues on the Streamlit GitHub repository. It's a testament to the open-source nature of Streamlit that such issues are identified, discussed, and resolved transparently.

Conclusion: Keeping Your Streamlit Apps Smooth

Experiencing deprecation warnings, especially when they seem to arise from standard usage, can be a bit jarring. The kwargs warning with st.plotly_chart and arguments like width="content" is a prime example. It's a sign that Streamlit is evolving, striving for cleaner internal practices, but sometimes these changes create temporary friction for users. The good news is that the Streamlit team is responsive, and this particular issue is recognized as a regression. By providing clear, reproducible examples and understanding the expected behavior, the community and the developers can work together to ensure that features like responsive chart sizing remain seamless. It's a continuous cycle of improvement, and your feedback is invaluable. For those looking to stay updated on Streamlit's development and engage with the community, the Streamlit GitHub repository is an excellent resource. You can find discussions, track issues, and even contribute to making Streamlit even better. Keep building those amazing applications, and rest assured that the Streamlit team is working hard to smooth out the rough edges!

For more in-depth information on Plotly configurations and best practices, you can refer to the official Plotly Documentation. And for understanding Streamlit's component API and development, the Streamlit Documentation is your go-to resource.