Streamlit Plotly Chart: Deprecation Warning Fix

If you've been building interactive dashboards with Streamlit and leveraging the power of Plotly charts, you might have recently encountered a rather persistent deprecation warning. Specifically, when using st.plotly_chart with parameters like width="content" or height, a warning pops up concerning kwargs. This can be quite confusing, especially when you're not explicitly passing any variable keyword arguments and are sticking to the documented parameters. It feels like getting a warning for something you haven't actually done wrong, right? Well, let's dive into what's happening and how to navigate this.

Understanding the kwargs Warning in st.plotly_chart

The core of the issue lies in how Streamlit handles arguments passed to st.plotly_chart. Previously, parameters like width and height might have been treated in a way that triggered a more general warning about variable keyword arguments (kwargs). The Streamlit developers have been actively working on refining the API to be clearer and more robust. As part of this effort, they introduced changes to how keyword arguments are handled to deprecate less flexible approaches and encourage more explicit ones. The warning you're seeing, "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 a sign of this ongoing refinement. It's designed to nudge users towards the more structured config parameter for Plotly-specific settings. However, it seems that even when using the intended width="content" parameter, which is a documented and valid way to control chart dimensions, the internal logic is still triggering this warning. This is a bit of a false alarm for users who are following best practices, and it's something the Streamlit team is aware of and working to address. The goal is to ensure that users only see warnings when they are actually using deprecated features, not when they are using the API as intended. This particular situation arose from a specific change in how st.plotly_chart processed its arguments, aiming to centralize Plotly-specific configurations within the config dictionary. While this change brings better organization for advanced use cases, it inadvertently cast a wider net for warnings, catching legitimate uses of width and height adjustments.

Why is This Happening?

The deprecation warning is triggered because of a recent update in Streamlit's argument handling. In versions prior to this change, using parameters like width="content" might have been processed in a way that didn't flag the kwargs warning. However, with the introduction of more structured argument parsing, particularly to encourage the use of the config parameter for Plotly-specific options, the internal mechanism now flags any use of kwargs that isn't explicitly the config dictionary. The warning message itself, "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 a clear indicator that Streamlit is moving towards a more organized way of passing settings. For Plotly charts, many fine-grained controls that you might have previously passed as direct keyword arguments are now expected to be nested within the config dictionary. This is a good practice for complex applications where you might have many Plotly-specific settings to manage, as it keeps the main function call cleaner. However, in this specific instance, it appears that even standard parameters like width and height, when set to specific values like "content", are being caught by this broader kwargs check. It's not that you're incorrectly using kwargs; rather, the system is interpreting the way these parameters are passed as potentially falling under the umbrella of variable keyword arguments that are being deprecated. This is a common challenge in software development: updates designed to improve clarity and structure can sometimes have unintended side effects on existing, perfectly valid use cases. The Streamlit team's intention is to streamline the API, but the implementation has, in this case, led to a misleading warning for users who are simply trying to adjust the size of their charts using documented features. The development team is actively looking into this to ensure the warning is only shown when truly necessary.

Reproducing the Warning: A Simple Example

To illustrate, let's look at the provided reproducible code example. It's quite straightforward and highlights the issue effectively:

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 you run this code in a Streamlit application (version 1.50.0 or similar), you'll observe the deprecation warning, even though you haven't explicitly passed any arbitrary kwargs to st.plotly_chart. The width="content" argument is a documented feature designed to make your charts responsive to their container. Yet, the warning about deprecated kwargs surfaces. This code snippet is minimal and focuses solely on generating a basic Plotly figure and then displaying it using st.plotly_chart with the width="content" parameter. The fig.update_layout also sets explicit width and height, which are properties of the Plotly figure itself, not arguments to st.plotly_chart. The crucial part is the st.plotly_chart(fig, width="content") line. This is where the interaction between Streamlit's plotting function and the underlying Plotly object occurs, leading to the warning. The expected behavior is that setting width="content" should simply adjust the chart's width to fill its container without raising any warnings about argument deprecation. The fact that it does is the core of the reported issue. It signifies that the warning mechanism is perhaps too broad or misinterpreting the intent of this specific parameter. The developers have identified this as a potential regression, meaning it worked as expected in an earlier version and has since started showing this misleading warning. The simplicity of the reproducible example is key to demonstrating that the warning isn't caused by complex or incorrect usage, but rather by the way Streamlit handles standard charting parameters.

Expected vs. Current Behavior

The Ideal Scenario: What We Expect

Ideally, when you use st.plotly_chart with documented parameters like width="content", the chart should render correctly without any deprecation warnings. The documentation clearly indicates that width="content" is a valid way to control the chart's responsiveness. This parameter is intended to automatically adjust the chart's width to fit its containing element, providing a seamless user experience. Therefore, the expected behavior is that Streamlit recognizes this parameter, applies the desired sizing, and proceeds without unnecessary warnings. The warning itself is about the deprecation of variable keyword arguments, implying that passing arbitrary, un-documented keyword arguments is discouraged. When you pass width="content", you are using a documented, specific parameter, and thus, no warning should be issued. This aligns with the principle of providing clear and actionable feedback to developers; warnings should highlight actual issues or impending removals of features, not interfere with standard usage. The user should be able to confidently use the documented features of the library without being sidetracked by confusing or irrelevant warnings. In essence, the expected behavior is a clean execution where the charting functionality works as advertised, and the developer receives guidance only on genuinely deprecated practices.

The Reality: What We're Seeing

Currently, even when using width="content", a deprecation warning related to kwargs is displayed. This warning suggests that variable keyword arguments are deprecated and recommends using the config argument instead. As highlighted in the issue details, the problematic code snippet within Streamlit likely 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."
    )

The issue is that the width="content" parameter, when passed to st.plotly_chart, is being caught by this if kwargs: condition. This means that even though width is a specific, documented parameter, Streamlit's internal logic is treating it as part of the general kwargs that the warning targets. This creates a confusing user experience, as developers are warned about using a feature that is explicitly supported. This is particularly problematic if this is a recent change, making it a regression from previous versions where this did not occur. The current behavior deviates from the expected outcome, leading to a need for clarification and a fix to ensure the warning system is accurate and helpful, rather than a source of confusion. It implies that the kwargs check might be too broad and needs to be refined to exclude known, documented parameters that are not truly