Fix Plotly Chart Width Deprecation Warning

by Alex Johnson 43 views

When working with Streamlit, we often want to fine-tune the appearance of our visualizations. One common requirement is to control the width of a displayed Plotly chart. You might have noticed a deprecation warning popping up, especially when using st.plotly_chart with parameters like width="content". This can be a bit confusing, as you're using documented parameters, yet a warning about variable keyword arguments (kwargs) appears. Let's dive into why this happens and what it means for your Streamlit applications.

The Curious Case of the kwargs Warning

The core of the issue lies in how Streamlit handles arguments passed to its components. When you use st.plotly_chart(fig, width="content"), you are providing a specific argument, width, to control the chart's dimensions. However, behind the scenes, Streamlit's internal mechanisms might be interpreting or processing these arguments in a way that triggers a general warning about the use of kwargs. This warning, which states, "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 intended to guide users away from passing arbitrary, undocumented keyword arguments directly to the st.plotly_chart function. The intention is to encourage the use of the config dictionary for Plotly-specific settings, which is a cleaner and more organized approach.

However, in some versions of Streamlit, this warning is being incorrectly triggered even when only documented parameters like width or height are used. This isn't ideal because it can cause unnecessary concern for developers who are adhering to the documentation. It suggests a potential mismatch between Streamlit's internal argument parsing and the user's intended usage. The good news is that this is often an indicator of an implementation detail rather than a fundamental problem with how you're using the width parameter. The developers are aware of such issues and work to refine the warning's conditions to be more precise.

It's important to understand that Streamlit is a rapidly evolving framework. Features are added, and existing ones are refined to improve performance, usability, and developer experience. Deprecation warnings are a standard part of this process. They serve as helpful nudges, alerting you to upcoming changes so you can adapt your code proactively. In this particular case, the warning about kwargs is a broader message about how configuration options should be handled. While it's not directly about the width parameter itself, the way width is passed and processed can sometimes fall under the umbrella of what triggers this general kwargs warning.

The core problem is that the warning is too broad and can be misleading. It implies that you are doing something wrong with kwargs when, in reality, you are likely using a standard, documented feature. This can lead to a frustrating debugging experience. Developers might spend time trying to eliminate kwargs when the issue is more about how Streamlit's internal checks are being performed. The ideal scenario is that this warning only appears when genuinely arbitrary kwargs are passed, and not when using parameters explicitly designed for controlling chart layout and dimensions.

This behavior has been observed in specific versions, like Streamlit 1.50.0, on macOS with Chrome. This indicates that the issue might be tied to specific operating system or browser interactions, or simply a bug in the argument parsing logic of that particular Streamlit release. Understanding this context helps to clarify that it's not necessarily a problem with your code's logic, but rather with the framework's reporting.

Why is This Happening? (A Deeper Look)

Let's consider the code example provided: st.plotly_chart(fig, width="content"). Here, width="content" is a parameter designed to make the Plotly chart dynamically adjust its width to fit the container it's placed in. This is a very useful feature for creating responsive dashboards. The plotly_chart function in Streamlit is a wrapper around Plotly's rendering capabilities, and it needs to manage various configurations. When you pass width="content", Streamlit is essentially telling Plotly how to render the chart. The deprecation warning about kwargs seems to stem from an internal check within Streamlit. This check might be looking for any unexpected keyword arguments passed to the underlying Plotly rendering engine or even within Streamlit's own function signature. If width or height are not explicitly handled as separate, named arguments in all internal processing steps, they might be caught by a more general kwargs check.

Think of it like a bouncer at a club. The bouncer has a list of specific people who are allowed in (documented parameters like width, height, use_container_width). But the bouncer also has a general rule: "No unsolicited guests" (arbitrary kwargs). In this scenario, the width="content" parameter, though valid, is somehow triggering the "unsolicited guest" alarm, even though it's actually on the guest list. This suggests the bouncer's alarm system is a bit too sensitive or not perfectly configured.

Streamlit's internal architecture involves passing information between Python and the frontend (where the chart is actually displayed). Arguments like width need to be correctly translated and passed along. If the translation process or the way Streamlit checks for valid arguments has a slight hiccup, it could lead to this warning. The deprecation of use_container_width in favor of width and height parameters for direct control is a good example of Streamlit evolving its API to be more explicit and user-friendly. However, sometimes these API changes can lead to transitional issues like the one observed with the kwargs warning.

The underlying Plotly library itself has a vast number of configuration options. Streamlit aims to provide a simplified interface. The config argument is specifically designed to pass these finer-grained Plotly options. By introducing a general kwargs warning, Streamlit is trying to steer developers towards this structured config approach for anything beyond the basic st.plotly_chart parameters. However, the current behavior is that this warning fires even for parameters that are meant to be directly used, which is a bug that needs addressing. It's a good reminder that even in well-designed libraries, edge cases and unintended consequences can arise, and it's the community's feedback that helps identify and fix them.

Expected vs. Current Behavior

Let's be clear about what we expect and what's currently happening. The expected behavior is that when you correctly use documented parameters for st.plotly_chart, such as width="content" or height=360, you should not see any deprecation warnings related to kwargs. The function should simply render the chart with the specified dimensions. The transition from use_container_width to width and height was intended to be smooth, and this includes suppressing misleading warnings.

The current behavior, as reported, is that using st.plotly_chart(fig, width="content") results in a deprecation warning about kwargs. This happens even though width is a valid parameter and no other arbitrary keyword arguments are being passed. This is problematic because it can make developers think they are doing something wrong when they are not. It's a regression because, in previous versions, this specific usage would not have triggered such a warning.

The root of the current behavior seems to be an overly broad condition in Streamlit's internal logic. The code snippet if kwargs: combined with the warning message suggests that if any keyword arguments are present (even if they are documented and expected ones like width), the warning might be triggered. This is not the intended functionality. The warning should ideally only activate when undocumented or arbitrary kwargs are passed, or when parameters that have been explicitly superseded (like use_container_width) are used without the new alternatives.

It’s a common challenge in software development to create robust argument parsing and warning systems. The goal is to provide helpful feedback without overwhelming or misleading the user. In this instance, the warning is serving more as a source of confusion than as helpful guidance. The fix would involve refining the condition that triggers the warning to be more specific about what constitutes an inappropriate use of kwargs.

This discrepancy highlights the importance of thorough testing after API changes. When a function's behavior is modified, especially concerning how it handles arguments and provides warnings, it's crucial to verify that all intended use cases still function as expected and that no unintended side effects, like false warnings, are introduced. The fact that this is marked as a regression further emphasizes that a previous version behaved correctly, and this issue was introduced during an update.

Reproducible Example and Steps to Reproduce

To help illustrate the problem, a clear and reproducible code example has been provided:

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 this simple script is run within a Streamlit application, the st.plotly_chart function is called with a Plotly figure and the width="content" argument. According to the issue report, this specific call triggers the kwargs deprecation warning, despite width being a documented and intended parameter for controlling the chart's responsiveness.

The steps to reproduce are straightforward:

  1. Ensure you have a Streamlit version where this issue exists (e.g., 1.50.0).
  2. Install the necessary libraries: streamlit and plotly.
  3. Create a Python file (e.g., app.py) and paste the provided code example into it.
  4. Run the Streamlit application from your terminal using the command: streamlit run app.py.
  5. Observe the output in your browser. You should see the Plotly chart rendered, and accompanying it, the deprecation warning related to kwargs will be displayed.

This clear reproducibility is invaluable for the Streamlit development team to pinpoint the exact cause of the warning and implement a fix. It confirms that the issue is not dependent on complex data or intricate plot configurations but rather on the fundamental way st.plotly_chart handles certain dimensional arguments.

Debugging Information Provided

The report also includes crucial debugging details that help narrow down the environment in which this issue occurs:

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

This information is vital. It suggests that the bug might be specific to certain configurations. For instance, it could be a platform-specific issue on macOS, a browser-specific rendering quirk, or indeed, a bug that was introduced in Streamlit version 1.50.0 and might have been present in subsequent or preceding versions as well. Developers can use these details to try and replicate the exact environment and thus more easily identify the faulty code path. Knowing the versions of Python and the OS helps rule out compatibility issues with those components and focus on Streamlit's implementation.

This detailed reporting, from the reproducible code to specific environment details, is exactly what makes the open-source development process so effective. It empowers the community to contribute to improving the tools they rely on.

Moving Forward: Addressing the Warning

While the Streamlit team works on a permanent fix, there are a couple of ways to approach this warning. The most direct solution is to wait for an updated version of Streamlit that corrects this behavior. Often, such issues are resolved in subsequent patch or minor releases. You can keep an eye on the Streamlit release notes.

Another, though less ideal, approach is to suppress the warning if it becomes too distracting. However, this is generally not recommended as it can mask other legitimate warnings. It's better to address the root cause.

For developers who need to integrate this functionality immediately and cannot afford to see the warning, they might consider reverting to a previous Streamlit version where this issue did not occur, though this is also a temporary and often impractical solution.

The long-term solution is for the Streamlit developers to refine the logic that triggers the kwargs deprecation warning. It needs to be more discerning, only firing when truly arbitrary or superseded arguments are passed, and not when standard, documented parameters like width are used. The goal is to ensure that warnings are always informative and accurate, contributing positively to the developer experience.

This situation is a good reminder of the continuous improvement cycle in software development. Feedback from users is essential for identifying bugs and usability issues. The Streamlit community's diligent reporting of such problems is what helps the framework evolve into a more robust and user-friendly tool for building data applications.

For more information on Streamlit and its features, you can always refer to the official documentation. Understanding the recommended ways to configure Plotly charts within Streamlit, particularly regarding the config dictionary for advanced settings, will ensure you're leveraging the library's capabilities effectively and are prepared for future updates.

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