Fixing Plotly Chart Deprecation Warnings

Hello there! Have you ever been happily plugging away at your Streamlit application, creating some awesome visualizations with Plotly, only to be met with a cryptic deprecation warning? It can be a bit jarring, especially when you feel like you're doing everything by the book. One such warning that has popped up for some users relates to kwargs in st.plotly_chart, even when you're not explicitly passing any variable keyword arguments. Let's dive deep into this and figure out what's going on and how to resolve it.

Understanding the kwargs Deprecation Warning in st.plotly_chart

So, what exactly is this kwargs deprecation warning all about? In Python, **kwargs is a special syntax used to pass a variable number of keyword arguments to a function. Essentially, it allows a function to accept any number of named arguments. In the context of Streamlit's st.plotly_chart function, the developers introduced a change to handle arguments passed to it. The warning message itself provides a clue: "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 triggered when Streamlit detects that kwargs are being used, even if you're just specifying parameters like width='content' or height='auto', which are documented and intended for use.

The core of the issue lies in how Streamlit is interpreting these parameters. Even though width and height are valid and documented arguments for st.plotly_chart, the underlying mechanism that checks for arbitrary kwargs is flagging them. This means that when you use st.plotly_chart(fig, width='content'), Streamlit sees width='content' as part of the kwargs being passed. If the code has a check like if kwargs: show_deprecation_warning(...), and kwargs is not empty (because it contains width), the warning is displayed. This is happening despite width being a legitimate, non-deprecated argument. It's a bit like a security guard seeing a bag (kwargs) and assuming it might contain something suspicious, even if it just holds your lunch.

This behavior is particularly frustrating because it muddies the waters. Users might think they are doing something wrong or using an undocumented feature when, in reality, they are using the API as intended. The goal of the deprecation warning is to guide users towards more current and supported ways of configuring plots, often by consolidating settings into a dedicated config dictionary. However, when legitimate, documented parameters get caught in this kwargs net, it creates confusion and unnecessary noise in the development process. It's important to remember that Streamlit is constantly evolving, and sometimes these changes, while intended to improve the library, can have unintended consequences or require a period of adjustment for users. The fact that this used to work in previous versions indicates that a change in how st.plotly_chart handles its arguments was implemented, perhaps to streamline argument parsing or to enforce a more structured way of passing Plotly-specific configurations.

Reproducing the Warning: A Simple Example

To really get a handle on this, let's look at a practical example. Suppose you're creating a barpolar chart using Plotly and want to control its width directly within Streamlit. Here’s how you might do it:

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 basic Plotly figure and then display it using st.plotly_chart. We specifically pass width="content". The intention here is to have the chart occupy the full width of its container, a common and useful setting. However, upon running this code in Streamlit versions where this behavior is present (like 1.50.0), you'll likely see a deprecation warning appear in your Streamlit app's output. This warning arises because, as we discussed, Streamlit's internal argument handling mechanism is identifying width="content" as part of kwargs and is triggering the deprecation warning associated with variable keyword arguments.

The expected behavior, as per Streamlit's documentation, is that using documented parameters like width and height should not result in a deprecation warning. These parameters are part of the public API, and developers should be able to use them without triggering warnings about deprecated kwargs. The warning suggests using the config argument for Plotly configuration options, which is a valid approach for passing specific Plotly settings. However, width and height are Streamlit-specific arguments for controlling the display dimensions of the chart within the app, not Plotly's internal layout settings.

The current behavior, which is the appearance of the warning, indicates a mismatch between how Streamlit's argument parsing works and the user's expectation based on the documentation. It's a regression because, in previous versions, this usage did not produce the warning. This suggests that a recent update might have altered the way st.plotly_chart processes its arguments, inadvertently causing documented parameters to be treated as general kwargs that are subject to deprecation checks.

Understanding this reproduction is key to appreciating the problem. It's a straightforward use case that, due to an implementation detail, leads to an undesirable warning. This highlights the importance of clear and robust argument handling in software libraries.

Why This Matters: User Experience and Code Clarity

This isn't just a minor annoyance; it's an issue that impacts the user experience and the clarity of your code. When you encounter a deprecation warning, especially one that seems to contradict the documentation, it can lead to a few unhelpful outcomes. Firstly, it can cause developer hesitation. You might pause your workflow, wondering if you're using the st.plotly_chart function incorrectly, or if you need to refactor your code immediately. This uncertainty can slow down development. Secondly, it can clutter your console or app output. Imagine a busy dashboard with multiple charts; a stream of these warnings can make it difficult to spot genuine errors or important log messages. This noise pollution can be detrimental to debugging and monitoring.

Furthermore, deprecation warnings are meant to be helpful guides, pointing you toward better practices. When they are triggered by standard, documented usage, they lose their effectiveness. Developers might start to ignore all warnings, including potentially critical ones, simply because they've become accustomed to seeing false positives. This is a dangerous habit to develop. The width="content" parameter, for instance, is a very practical way to ensure your charts are responsive and fit well within different screen sizes or layouts. It's a feature that users should be encouraged to use, not one that should be flagged as potentially problematic.

The distinction between Streamlit-specific arguments and Plotly-specific configurations is crucial here. Streamlit provides arguments like width, height, and use_container_width to control how a chart is rendered within the Streamlit app environment. Plotly, on the other hand, has its own extensive set of layout and configuration options that can be passed via the config argument. The deprecation warning seems to be conflating these, treating Streamlit's display control arguments as if they were Plotly configuration parameters that should be managed through the config dictionary.

The fix for this issue is not about users learning a new way to set width or height, but rather about Streamlit's internal logic correctly distinguishing between its own arguments and those intended for Plotly. When a user specifies width='content', they are telling Streamlit how wide the chart element should be in the app, not trying to configure a Plotly trace or layout property. The current behavior, where this valid Streamlit argument triggers a deprecation warning about kwargs intended for Plotly configuration, is a bug that needs to be addressed by the Streamlit developers. It’s about ensuring the library behaves as documented and doesn’t inadvertently penalize users for using its features correctly.

Looking Ahead: Solutions and Best Practices

While the Streamlit team is likely working on a definitive fix for this kwargs deprecation warning issue, there are a couple of ways you can navigate this in the meantime. One approach is to temporarily suppress the specific warning if it's hindering your development and you're confident in your usage. However, this should be done with caution, as you don't want to mask other important warnings.

A more robust solution, and one that aligns with the spirit of the deprecation warning, is to understand and utilize the config argument effectively for Plotly-specific settings. Although width and height for the display of the chart are Streamlit concerns, Plotly itself has many configuration options that are best passed through the config dictionary. For example, if you wanted to control Plotly's behavior like enabling downloadable images or modifying hover behavior, you'd use:

config = {
    "toImageButtonOptions": {
        "format": "svg",
        "filename": "my_plot",
        "height": 500,
        "width": 700,
        "scale": 1
    },
    "displaylogo": False
}

st.plotly_chart(fig, config=config)

This correctly uses the config argument for Plotly's internal settings, avoiding the kwargs warning for these specific cases. The problem at hand, however, is not with these kinds of configurations but with Streamlit's own width and height parameters.

The ideal solution will come from Streamlit itself, where the st.plotly_chart function is updated to correctly differentiate between its own parameters (like width, height) and the arbitrary kwargs that should be passed to Plotly via the config argument. This would involve modifying the internal logic to not flag documented arguments as general kwargs that trigger the deprecation warning. Until then, being aware of this specific quirk and perhaps noting it in your project documentation can save you and your team some debugging time.

Remember, the goal is to make your Streamlit applications robust and easy to maintain. Understanding these nuances, even temporary ones, is part of becoming a proficient Streamlit developer.

External Resources for Further Learning

For those who want to dig deeper into Streamlit and Plotly integration, or understand deprecation best practices, here are some valuable resources:

• Streamlit Documentation: For the most up-to-date information on st.plotly_chart and its arguments, the official Streamlit documentation is your best friend. You can find details on how to pass configurations and manage chart display. [Streamlit Documentation](https://docs.streamlit.io/library/api-reference/ செல)
• Plotly Python Graphing Library: To understand the full capabilities of Plotly charts and their configuration options, refer to the Plotly documentation. This will help you distinguish between Streamlit's rendering controls and Plotly's internal settings. Plotly Python Documentation

By staying informed and understanding the underlying mechanisms, you can build more effective and reliable data applications.