Streamlit Plotly_chart Kwargs Deprecation Warning Fix

If you're a Streamlit user working with interactive plots, you might have encountered a peculiar warning message when using st.plotly_chart. This warning pops up concerning kwargs (keyword arguments) deprecation, even when you're confident you haven't passed any explicit variable keyword arguments and are strictly using documented parameters. It can be a bit confusing, right? Let's dive deep into what's happening, why it's occurring, and how to navigate it smoothly. We'll explore the scenario, provide a clear reproducible example, and discuss the expected versus current behavior, ensuring you can continue building amazing data visualizations without unnecessary alerts.

The Nuance of st.plotly_chart and Kwargs

When Streamlit introduced changes to how keyword arguments are handled, especially concerning the st.plotly_chart function, the goal was to streamline its API and encourage the use of more explicit configuration options. The plotly_chart function is your gateway to embedding rich, interactive plots generated by Plotly.js directly into your Streamlit applications. Plotly itself is a powerful library for creating dynamic and beautiful charts, and Streamlit makes it incredibly easy to integrate these into your web apps with just a few lines of Python code. However, like any software, as features evolve and best practices shift, some older ways of doing things might become deprecated. This is where the kwargs deprecation warning comes into play. It's a heads-up from the Streamlit team that a particular method of passing arguments might be phased out in future versions, encouraging developers to adopt newer, more robust methods. The core of the issue arises when you use parameters like width="content" or height="content" within st.plotly_chart. While these are perfectly valid and documented ways to tell Streamlit to adjust the chart's dimensions based on its content, the underlying implementation might be triggering this warning. It seems that even when you're using these documented parameters, the function's internal handling of arguments is being flagged by the new deprecation checks. This can be misleading because the warning suggests that you are doing something wrong with variable keyword arguments, when in reality, it's an artifact of how the function processes its arguments, potentially related to how it passes them down to Plotly or manages its own internal state. Understanding this distinction is crucial for debugging and for ensuring your code is future-proof.

Reproducing the Warning: A Clear Example

To truly understand this deprecation warning, let's walk through a reproducible code example. This snippet demonstrates how the warning can surface even with straightforward usage of st.plotly_chart. We'll import the necessary libraries, create a simple Plotly figure, and then display it using Streamlit's plotly_chart function, intentionally using the width="content" argument.

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")

In this code, we first set up a basic plotly.graph_objects.Figure. We add a single barpolar trace, which is just a simple element for demonstration. We also set explicit width and height in update_layout, though these are internal Plotly layout parameters and don't directly affect how Streamlit renders the chart initially. The key line is st.plotly_chart(fig, width="content"). Here, we're telling Streamlit to automatically determine the width of the chart container based on the content it holds. This is a convenient feature, especially when you want your plots to be responsive. However, it's precisely this use of width="content" that seems to trigger the kwargs deprecation warning. The warning appears because Streamlit's internal logic for handling arguments passed to plotly_chart is catching this specific parameter, perhaps as it's being processed or forwarded, and is issuing the deprecation notice. It's important to note that you are not explicitly passing **kwargs in the Python sense here; you are using a documented, named argument. This points to a potential subtlety in how Streamlit's argument parsing interacts with Plotly's rendering, leading to an unintended warning message.

Expected vs. Current Behavior: What Should Happen?

The expected behavior when using st.plotly_chart with documented parameters like width="content" is, quite simply, that it should work without raising any deprecation warnings. The documentation clearly outlines that width and height are valid arguments that can be passed to st.plotly_chart to control the display dimensions. When you use width="content", Streamlit is expected to intelligently size the plot to fit its container. This is a desirable feature for creating adaptable dashboards and applications. The deprecation warning specifically mentions that "Variable keyword arguments for st.plotly_chart have been deprecated and will be removed in a future release. Use the config argument instead." This implies that any non-standard or variable keyword arguments passed should trigger this warning, guiding users towards the config dictionary for Plotly-specific settings. However, the current behavior is that this warning is erroneously triggered even when using the documented width argument. This suggests a disconnect between Streamlit's argument validation and its actual implementation for handling chart dimensions. The warning is being emitted because the internal code path that checks for kwargs is being activated by the width="content" parameter, even though width is a recognized and supported argument for st.plotly_chart. This creates confusion for users who are following the documentation and still receive a warning that seems to imply they are misusing the function. It's a situation where the warning mechanism is too broad or is being triggered by an internal detail that doesn't reflect actual misuse by the end-user.

Why Is This Happening? A Deeper Look

Understanding why this kwargs deprecation warning occurs, especially when using documented parameters like width="content", requires a peek under the hood of Streamlit's st.plotly_chart function. The warning itself is triggered by a specific piece of code introduced to manage the transition away from using variable keyword arguments for certain Plotly configurations. The relevant snippet often looks something like this:

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 block is designed to catch any arguments passed to st.plotly_chart that are not explicitly defined parameters of the function itself. The intention is to guide users towards using the config dictionary for passing Plotly-specific options, which offers a more structured and future-proof way to manage Plotly's extensive settings. However, the issue arises because the width and height parameters, when set to a string value like "content", might be processed in a way that, internally, they are being treated as part of the kwargs that the deprecation check is looking for. It's not that you are explicitly writing **kwargs in your code; rather, the Streamlit function might be receiving width='content' and then, in its internal processing, this argument (or how it's handled before being passed to Plotly) is being caught by the generic if kwargs: check. This could be due to how Streamlit maps its own parameters to Plotly's internal configuration or how it handles dynamic sizing requests. The check might be too aggressive, flagging valid, documented Streamlit arguments that happen to be passed through a path that resembles variable keyword arguments. This is why the warning appears even when you're using parameters that are officially supported and documented for st.plotly_chart.

Is This a Regression?

Yes, this is indeed a regression. In previous versions of Streamlit, using the width and height arguments with values like "content" in st.plotly_chart functioned as expected without triggering any deprecation warnings. The ability to dynamically size charts based on their content was a supported and useful feature. The introduction of the kwargs deprecation warning, while intended to improve the API's long-term maintainability and guide users towards best practices, has inadvertently broken this functionality for users who rely on it. This means that if you've recently updated Streamlit, you might suddenly see this warning appear for code that previously ran without issues. This regression highlights the importance of thorough testing during software updates, particularly when changes are made to argument parsing or internal function behavior. Developers who encounter this issue are effectively seeing a step backward in functionality or user experience, as the warning serves as a false alarm, disrupting the clean execution of their Streamlit applications.

Debugging and Moving Forward

When faced with this Streamlit deprecation warning, the first step is to recognize that it's likely not an error in your code but rather a quirk in Streamlit's current implementation. While the warning suggests using the config argument for Plotly settings, for width="content" or height="content", this might not be the direct solution to suppress the warning itself, as these are Streamlit-specific layout parameters, not Plotly configurations. If you need to suppress the warning entirely and are comfortable with the behavior, you might explore ways to filter warnings or temporarily disable them, though this is generally not recommended for long-term solutions. The ideal resolution, however, lies with the Streamlit developers addressing this specific case. They need to refine the deprecation check to differentiate between actual variable keyword arguments and documented parameters like width and height when used in st.plotly_chart. Until a fix is implemented in a future Streamlit release, users might have to tolerate the warning or seek alternative ways to manage chart sizing if the warning proves too disruptive. For now, knowing that your code is likely correct and the warning is a false positive is the most important takeaway.

Conclusion: Navigating Plotly Charts in Streamlit

Dealing with deprecation warnings can sometimes feel like navigating a maze, especially when they appear for perfectly valid code. The kwargs deprecation warning in st.plotly_chart when using width="content" is a prime example of such a situation. It's a reminder that libraries evolve, and while the intention behind such warnings is to guide us toward better practices, the implementation can occasionally lead to false alarms. We've seen that this warning is triggered by Streamlit's internal argument handling, not by a direct misuse of variable keyword arguments by the user. The code example clearly illustrates the scenario, and understanding the expected versus current behavior clarifies that this is a regression. While Streamlit works diligently to provide a stable and evolving platform, occasional hiccups like this are part of the development process. For now, the best approach is to be aware of this specific warning, recognize that your code is likely functioning correctly, and look forward to a future Streamlit update that rectifies this behavior. In the meantime, for further insights into Streamlit and its advanced features, you can always refer to the official Streamlit Documentation. For deeper dives into Plotly's capabilities, the Plotly Python documentation is an invaluable resource.