Streamlit Plotly Chart Width Warning Fix

by Alex Johnson 41 views

It's a common frustration when you're building a Streamlit app and encounter unexpected warnings. You've followed the documentation, used the parameters as intended, and yet, a deprecation warning pops up, making you question if you're doing something wrong. This is precisely the situation some Streamlit users have found themselves in when using the st.plotly_chart function with the width='content' (or height='content') argument. This issue, where using documented parameters like width='content' incorrectly triggers a deprecation warning related to variable keyword arguments (kwargs), has caused confusion and a bit of unnecessary alarm among developers. The warning suggests that variable keyword arguments are deprecated and users should use the config argument instead. However, when the width or height arguments are used as intended, no variable keyword arguments are actually being passed. This leads to a confusing experience, as the warning appears to be misfiring, indicating a potential bug or a misunderstanding in how the warning is being triggered.

Understanding the plotly_chart Deprecation Warning

The plotly_chart function in Streamlit is a powerful tool for embedding interactive Plotly visualizations directly into your web applications. To enhance its flexibility and align with evolving Python practices, Streamlit has been updating how it handles arguments. Recently, there have been changes related to how variable keyword arguments (**kwargs) are managed. The intention behind these changes is to encourage more explicit and documented ways of passing configurations to the Plotly charts, primarily through the config argument. This is a good practice, as it makes the code more readable and maintainable. However, the implementation of this change seems to have inadvertently caused a side effect. The specific problem arises when users leverage the width='content' or height='content' arguments within st.plotly_chart. These arguments are documented and intended for use to automatically adjust the chart's dimensions to fit its container. Yet, instead of just rendering the chart, Streamlit is issuing a deprecation warning, stating 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." This warning is misleading because, in this scenario, the user isn't actually passing arbitrary, undocumented keyword arguments. They are using a specifically documented parameter that controls the chart's layout. The warning is triggered because the internal logic of st.plotly_chart might be processing these layout arguments in a way that its warning mechanism interprets as an overuse of **kwargs, even when it's not.

The Impact of Misleading Warnings

Misleading deprecation warnings can have a ripple effect on development workflows. Firstly, they can lead to unnecessary investigation and debugging time. Developers might spend valuable minutes or even hours trying to figure out what they've done wrong, scrutinizing their code for undocumented kwargs that simply aren't there. This distracts from the actual task of building the application's features. Secondly, it can erode trust in the warning system. If warnings frequently appear to be false positives, developers may start to ignore them altogether, which could lead to them missing genuine, important deprecation notices in the future. This can also affect the perceived stability and polish of the Streamlit library itself. A library that appears to be issuing incorrect warnings might seem less reliable, even if the core functionality is working perfectly. For the specific case of st.plotly_chart and the width='content' argument, the expectation is straightforward: the chart should render with its width adjusted to fill the available space, and no warnings should appear. The current behavior deviates from this expectation, creating a suboptimal user experience. The goal of Streamlit is to make app development easy and intuitive, and this type of warning unfortunately works against that objective.

Reproducing the Issue: A Simple Code Example

To illustrate the problem clearly, let's look at a reproducible code example. This snippet demonstrates how to create a basic Plotly figure and display it using st.plotly_chart, specifically triggering the warning. The code involves importing the necessary libraries, creating a simple Plotly graph object, and then rendering it with the width='content' argument.

import plotly.graph_objects as go
import streamlit as st

# Create a sample Plotly figure
fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
fig.update_layout(width=500, height=360)

# Display the figure using st.plotly_chart with width='content'
st.plotly_chart(fig, width="content")

When you run this code in a Streamlit application, you will observe the deprecation warning. The code itself is straightforward and uses documented parameters. The fig.update_layout(width=500, height=360) part sets the figure's intrinsic dimensions, while st.plotly_chart(fig, width="content") instructs Streamlit to try and make the chart's display area adapt to the content's needs or the container's width. The issue is that the width="content" argument, which is a valid and documented way to control the chart's display size in Streamlit, is being caught by the kwargs deprecation check. This is likely because Streamlit's internal handling of arguments might be passing width and height in a way that the warning system interprets as arbitrary keyword arguments, rather than explicitly handled parameters. This example highlights the need for a precise fix to ensure that only truly variable and undocumented kwargs trigger the warning, preserving the clarity and reliability of Streamlit's feedback to developers.

The Expected vs. Current Behavior

In an ideal scenario, when you use st.plotly_chart with arguments like width='content' or height='content', the function should simply render the Plotly chart, automatically adjusting its size to fit the available space within the Streamlit app layout. The expected behavior is a seamless integration of the visualization without any accompanying warnings. The width='content' parameter is designed to be a helpful shortcut, allowing developers to avoid hardcoding pixel values and instead let Streamlit manage the responsiveness of the chart. It's a feature that enhances usability.

However, the current behavior contradicts this expectation. As demonstrated by the reproducible code example, using width='content' results in the following deprecation warning being displayed:

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 warning is problematic because, as mentioned, the user is not passing any variable keyword arguments. They are using a specific, documented parameter intended for layout control. The warning suggests using the config argument, which is typically for Plotly-specific options like scrollZoom or displayModeBar, not for controlling the overall width or height of the chart's container within Streamlit. This disconnect between the warning's message and the user's actual action is the core of the issue. It implies that the logic for detecting deprecated kwargs is too broad and is incorrectly flagging the use of the width and height arguments.

Is This a Regression?

Yes, this is indeed a regression. The issue description explicitly states that this behavior used to work in a previous version of Streamlit. This means that an update or a recent change in Streamlit's codebase has introduced this unwanted warning. Regressions are particularly troublesome because they can disrupt existing, functional applications. If an app was previously working without warnings, and a simple Streamlit update causes these warnings to appear, it forces developers to either ignore the warnings (risking missing real issues) or spend time investigating and potentially patching their code for something that was previously not a problem. The fact that it worked before indicates that the underlying mechanism for handling width and height was more robust or that the deprecation warning system has become overly sensitive. Identifying and fixing regressions is crucial for maintaining the stability and reliability of software libraries. Users expect that updating a library will either bring new features or fix bugs, not introduce new, misleading warnings into their stable applications. This regression highlights the importance of thorough testing, especially for how warnings are triggered and what conditions they respond to, to ensure that updates provide a net positive experience for the development community.

Debugging Information and Next Steps

To help pinpoint the exact cause and facilitate a fix, the following debugging information has been provided:

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

This information provides a snapshot of the environment where the issue is occurring. Streamlit version 1.50.0 is key here, as it suggests that the problem was introduced around this release. The Python version, OS, and browser are also relevant as they can sometimes influence rendering or behavior, though the warning itself seems to be a code logic issue within Streamlit.

What Needs to Be Done?

The primary goal is to correct the logic within st.plotly_chart so that the deprecation warning for variable keyword arguments (**kwargs) is only triggered when truly undocumented or variable keyword arguments are passed. Arguments like width and height, when used with their documented values ('content' or pixel values), should be handled correctly and not be flagged as deprecated kwargs.

Possible approaches to fix this could involve:

  1. Refining the kwargs detection: Ensure that the code checking for kwargs specifically excludes parameters that are explicitly defined and handled by st.plotly_chart itself, such as width and height.
  2. Revisiting argument parsing: Examine how width and height are processed internally. If they are being passed down to Plotly in a way that the kwargs warning mechanism detects, this process might need adjustment.
  3. Clarifying documentation (if needed): While the width='content' is documented, ensuring there are no subtle nuances in its usage that might be misinterpreted by the library is always a good step, though the provided example suggests this is unlikely.

The community and developers behind Streamlit will likely need to review the internal implementation of st.plotly_chart to identify the precise point where the width='content' argument is causing the kwargs warning to fire incorrectly. Addressing this regression will restore confidence in the warning system and improve the developer experience for users of st.plotly_chart.

Conclusion

The plotly_chart function is a cornerstone for interactive data visualization in Streamlit applications. The recent introduction of a deprecation warning for variable keyword arguments (kwargs) is a well-intentioned move towards cleaner code, but its current implementation has led to a frustrating experience for users employing the documented width='content' and height='content' parameters. This misleading warning acts as a regression, disrupting existing workflows and potentially causing developers to overlook genuine warnings in the future.

By providing a clear reproducible example and detailing the discrepancy between expected and current behavior, the Streamlit community can work towards a resolution. The fix should involve refining the kwargs detection logic to accurately distinguish between arbitrary keyword arguments and documented parameters used as intended.

Ultimately, the goal is to ensure that Streamlit's feedback mechanisms are precise and helpful, fostering a development environment where users can confidently build and deploy their applications without encountering spurious errors. Addressing this specific issue will reinforce the reliability and user-friendliness that Streamlit aims to provide.

For more insights into Plotly and its capabilities, you can explore the official Plotly Python documentation. For Streamlit-specific best practices, the Streamlit documentation is an invaluable resource.