Streamlit Plotly Chart: Fixing Deprecation Warnings

Hey there, fellow Streamlit enthusiasts! Let's dive into a common hiccup many of us have encountered recently when working with st.plotly_chart: that sometimes perplexing deprecation warning that pops up, even when you're just trying to set the width or height of your awesome Plotly visualizations. It can be a bit confusing, right? You're following the documentation, using the parameters as expected, and yet, there's that warning message staring back at you. We're here to unravel this mystery and get your Streamlit apps running smoothly without those pesky warnings.

Understanding the "kwargs" Deprecation Warning

So, what exactly is this "kwargs" deprecation warning all about? In the world of Python, **kwargs is a special syntax that allows a function to accept an arbitrary number of keyword arguments. These are arguments passed in the form of key=value. When Streamlit introduced changes to how st.plotly_chart handles its arguments, specifically around how it passes configurations to Plotly, a warning was implemented. This warning is triggered when the function thinks you might be passing variable keyword arguments (**kwargs) that are not explicitly documented or handled. The intention behind this warning is to encourage users to use the dedicated config argument for passing Plotly-specific configurations, rather than relying on general keyword arguments that might be ambiguous or change in the future. However, as many of you have noticed, this warning sometimes fires even when you're only using documented parameters like width="content" or height=300. This can be a bit of a red herring, making you think you're doing something wrong when, in fact, the library is just being a bit overzealous in its warning.

The core of the issue lies in how Streamlit's plotly_chart function processes arguments. When you call st.plotly_chart(fig, width="content"), you are passing width as a direct argument. However, internally, Streamlit's argument parsing might be designed in a way that it checks for any unassigned keyword arguments after processing the known ones. If it detects something that looks like an unhandled keyword argument, even if it's a documented one like width, it might trigger the warning. This is essentially a form of defensive programming to guide users towards the preferred config argument for advanced Plotly settings. The config argument is designed to be a dictionary that directly maps to Plotly's layout configuration options, providing a more robust and explicit way to customize your charts. While this is a good practice for complex configurations, it can be slightly inconvenient when simple parameters like width or height are involved. The goal of this discussion is to clarify this behavior and ensure that using standard, documented arguments like width and height does not inadvertently trigger a deprecation warning.

This situation can be particularly frustrating because it might lead developers to unnecessarily modify their code or spend time investigating what they perceive as an error. The ideal scenario is that documented parameters function as expected without triggering warnings related to internal argument handling. By understanding the underlying mechanism, we can better appreciate why this warning appears and how to potentially mitigate it, or at least understand that it's not necessarily an indication of a critical issue in your own code but rather a nuance in the library's implementation. The Streamlit team is continuously working to refine these warnings to be more precise and less intrusive, ensuring a smoother developer experience.

Reproducible Example and Expected Behavior

To make this issue crystal clear, let's look at the provided code example. It's a straightforward setup:

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 snippet, we create a simple Plotly figure and then display it using st.plotly_chart. The crucial part here is width="content". According to Streamlit's documentation, width and height are indeed valid arguments for st.plotly_chart to control the size of the displayed chart. The "content" value is particularly useful as it instructs Streamlit to size the chart based on the available space within its container, making your app responsive.

The Expected Behavior: Based on the official documentation, when you use st.plotly_chart with arguments like width="content", you should not receive any deprecation warnings. The function should simply render the chart with the specified width. The warning about kwargs should only appear if you are passing arbitrary, undocumented keyword arguments that are not being handled by the function. The use of documented parameters like width should be seamless.

The Current Behavior: However, as many users have observed, the current implementation often triggers a 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 warning appears precisely when you use width="content" (or height, for that matter), even though these are documented parameters. This means that the internal logic that checks for kwargs is incorrectly flagging the use of these standard arguments as potentially problematic.

This discrepancy between expected and current behavior is what makes this a significant point of discussion. It's not a matter of using the tool incorrectly; it's about the tool's feedback mechanism being a bit too sensitive. The team behind Streamlit is aware of this and is working to refine these warnings to be more accurate. The goal is to ensure that developers are only warned when they are truly using features that are deprecated or might cause issues, rather than being alerted by the use of standard, supported functionalities. This is a common challenge in software development where maintaining backward compatibility while introducing new features and best practices requires careful handling of warnings and deprecation notices. The aim is always to improve the developer experience and make the library more robust and intuitive over time.

Why This Matters: User Experience and Clarity

This particular deprecation warning issue, while seemingly minor, has a real impact on the user experience for Streamlit developers. When a warning pops up, especially one related to deprecation, it usually signals that a part of the code might be outdated or could cause problems in the future. This prompts developers to investigate, potentially leading them down a rabbit hole trying to fix something that isn't actually a problem with their code, but rather with how the library is interpreting standard usage.

Maintaining Code Clarity and Confidence

Developers strive for clean and understandable code. Receiving unexpected warnings can obscure the real issues within an application. If every use of width="content" or height=300 triggers a warning about kwargs, it becomes difficult to distinguish between a genuine deprecation that needs addressing and a false positive. This can erode confidence in the warning system itself and lead to developers ignoring warnings altogether, which is a dangerous practice. The goal of deprecation warnings is to provide a helpful nudge towards better practices, not to create noise that distracts from genuine problems.

The Importance of Documented Features

It's crucial that documented features work as described without triggering confusing warnings. The width and height arguments for st.plotly_chart are officially part of the API. When their usage leads to a warning that suggests using config instead, it creates ambiguity about the intended way to control chart dimensions. While config is indeed the preferred method for advanced Plotly configurations, simple dimension adjustments should ideally be straightforward. Streamlit's documentation should be the single source of truth, and its guidance should align with the library's behavior. This ensures that users can rely on the documentation to build their applications effectively.

Encouraging Best Practices Correctly

Streamlit's intention to guide users towards the config argument for Plotly configurations is a good one. The config dictionary allows for more granular control over Plotly's behavior, such as enabling or disabling interactivity, setting responsive behavior, or customizing tooltips. However, the warning mechanism should be precise. It should only trigger when kwargs are actually being used in a way that conflicts with the intended API or when a parameter is truly being deprecated. In cases like width="content", the warning is misleading because it suggests a problem where there isn't one, and it doesn't accurately reflect the nature of the argument being passed. A more accurate warning might specify that while width is accepted, for more complex settings, config is recommended. This nuanced approach helps developers understand the best practices without causing unnecessary alarm.

Ultimately, the goal is to have a Streamlit experience that is both powerful and intuitive. This means that the tools and feedback mechanisms provided should be as clear and accurate as possible. Addressing this specific kwargs deprecation warning will contribute to a more streamlined development process and a greater sense of clarity for anyone building data visualizations with Streamlit and Plotly.

Moving Forward: Solutions and Best Practices

While the Streamlit team works on refining the warning system, there are ways to navigate this situation and continue building your applications effectively. Understanding the nuances of how Streamlit handles arguments for st.plotly_chart can help you make informed decisions.

Understanding the config Argument

The warning message correctly points towards the config argument as the modern way to pass Plotly-specific configurations. The config argument expects a dictionary where you can specify various Plotly options. For example, if you wanted to control interactivity or other advanced Plotly features, you would use it like this:

st.plotly_chart(fig, config={
 "displaylogo": False,
 "modeBarButtonsToRemove": ["zoom2d", "pan2d"]
})

This approach is explicit and future-proof, as it directly maps to Plotly's configuration options. While width and height are simple parameters, if you find yourself needing more control over how your Plotly chart behaves within Streamlit, the config argument is the way to go. It's designed to handle a wide array of Plotly's client-side configurations, offering a robust solution for customizing your visualizations beyond just their dimensions.

Potential Workarounds and Future Expectations

For the immediate issue of the width="content" warning, here are a few thoughts:

1. Ignore the Warning (with caution): If you've confirmed that width and height are the only non-standard arguments you're passing and your application functions correctly, you might choose to temporarily ignore this specific warning. However, it's always best practice to keep an eye on deprecation warnings, as they do indicate upcoming changes. The fact that it's a regression suggests it might be addressed in a future update.
2. Use use_container_width (if applicable): In older versions of Streamlit, use_container_width=True was a common way to make charts responsive. While this has been superseded by the width argument with values like "content", understanding its history helps. The new width="content" is essentially the intended replacement.
3. Consider update_layout for Dimensions: Although st.plotly_chart accepts width and height arguments directly, you can also set dimensions within your Plotly figure itself using fig.update_layout(width=..., height=...). However, using width="content" in st.plotly_chart is specifically for making the chart responsive to its container, which update_layout doesn't achieve in the same way within a Streamlit app.

The Streamlit team is actively working on improving the clarity and accuracy of these warnings. As noted, this issue appears to be a regression, meaning it worked correctly in a previous version. This strongly suggests that it will be addressed in an upcoming release. When updating Streamlit, always check the release notes for information on bug fixes and improvements related to plotting components. The development community often benefits from clear bug reports like this one, which help prioritize fixes.

In conclusion, while the kwargs deprecation warning when using st.plotly_chart with width="content" might be a bit confusing right now, it's likely a temporary hiccup being ironed out. By understanding the purpose of the config argument and keeping an eye on Streamlit updates, you can ensure your applications remain robust and visually appealing. Remember, the goal is always to create dynamic and informative dashboards, and Streamlit, with its integration of powerful libraries like Plotly, is an excellent tool for achieving that.

For further insights into Plotly configurations and best practices, you might find the official Plotly documentation very helpful. Additionally, exploring the [Streamlit documentation on plotting](https://docs.streamlit.io/library/api-reference/ வெப்-components/st.plotly_chart) can provide more context on how Streamlit integrates with Plotly charts.