Streamlit Plotly Chart Kwargs Deprecation: Fix Width=content Warning

by Alex Johnson 71 views

Hey there, data visualization enthusiasts! Have you ever been happily plotting away with Streamlit and plotly_chart, only to be greeted by a slightly alarming deprecation warning? If you've tried using width="content" (or height="content") and seen a message about kwargs being deprecated, you're not alone. It can be a bit confusing, especially when you're not explicitly passing any variable keyword arguments. Let's dive into what's happening and how to navigate it.

Understanding the st.plotly_chart Kwargs Deprecation

Streamlit's st.plotly_chart is a fantastic tool for embedding interactive Plotly charts directly into your web applications. It's designed to be intuitive, allowing you to pass your Plotly figures and various display options. Recently, there have been updates to how st.plotly_chart handles arguments, particularly kwargs (keyword arguments). The team behind Streamlit is working to streamline the API, making it cleaner and more predictable for everyone. This often involves deprecating older methods in favor of newer, more robust ones. One such change involves how certain chart dimensions and configurations are handled. Historically, some parameters might have been accepted directly as kwargs that are now expected to be passed within a dedicated config argument. This is a common practice in software development to prevent ambiguity and ensure that parameters are used as intended. The goal is to make the API more explicit, meaning you know exactly where to put your configuration options. This can lead to a deprecation warning when a parameter, like width or height set to a string value such as "content", is still being processed through the general kwargs mechanism, even if you're not passing any other arbitrary kwargs.

The core of the issue lies in the internal implementation of st.plotly_chart. When you pass width="content", Streamlit needs to interpret this instruction and pass it along to the underlying Plotly chart. In some versions of Streamlit, this interpretation might still be happening through a general keyword argument handler. However, the Streamlit developers have introduced a specific mechanism for configuration options, usually via a config dictionary. If the width parameter, even when explicitly stated as width="content", is caught by the general kwargs check before it's properly routed to the dimension handling, it can trigger the deprecation warning. This warning is intended to guide users towards the new config parameter for all Plotly-related configurations, which is a good practice for future compatibility. 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 quite clear about the intended solution. It's not that your width="content" usage is fundamentally wrong, but rather that the way it's being processed might be triggering the warning mechanism designed to catch less structured keyword arguments. This can feel like a bug, especially if you're following the documentation for parameters like width and height which are listed as accepted arguments for st.plotly_chart.

It's important to remember that deprecation warnings are there to help you adapt your code before a feature is removed entirely. They act as signposts, guiding you towards the more current and supported way of doing things. In this case, Streamlit is gently nudging users to consolidate their Plotly-specific settings within the config argument. This helps maintain a cleaner interface and avoids potential conflicts with other arguments that st.plotly_chart might accept. So, while it might seem like a minor annoyance, it's a signal that the Streamlit API is evolving, and it's a good opportunity to align your code with the latest best practices. The reproducible example provided in the original issue clearly demonstrates this – a simple barpolar chart with width="content" throws the warning, even though width is a documented parameter. This suggests that the internal logic is flagging it as an unexpected kwargs usage.

Reproducible Example and Steps to Reproduce

Let's look at the code that triggers this warning. It’s quite straightforward and involves creating a basic Plotly figure and then displaying it with Streamlit:

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 environment (version 1.50.0 or similar, on Python 3.14.2 or any other compatible version), you'll likely see the deprecation warning appear alongside your chart. The steps to reproduce are simply:

  1. Import necessary libraries: plotly.graph_objects and streamlit.
  2. Create a Plotly figure: In the example, a go.Figure with a Barpolar trace is used. You can substitute this with any other Plotly chart.
  3. Update layout (optional but good practice): Setting width and height in update_layout is standard for Plotly figures.
  4. Display the chart using st.plotly_chart: Crucially, pass the width="content" argument to st.plotly_chart.

That's it! The warning should pop up. This behavior suggests that the width parameter, when set to a string like "content", is being interpreted as a general keyword argument that falls under the new deprecation policy, rather than a specific, documented parameter for st.plotly_chart itself.

This is particularly relevant because width and height are documented parameters for st.plotly_chart. The documentation often suggests using use_container_width=True as an alternative to achieve similar responsive behavior. However, width="content" offers a slightly different control, allowing the chart to size itself based on its content, which can be useful in certain layouts. The fact that this documented parameter triggers a deprecation warning indicates a potential mismatch between Streamlit's internal handling and its public API documentation, or at least an unintended consequence of the kwargs refactoring. The warning is specifically looking for variable keyword arguments, and it seems that width="content" is being caught in this net, even though it's a named, intended parameter.

Expected vs. Current Behavior: What's Going Wrong?

The behavior we expect when working with Streamlit's st.plotly_chart and trying to control the width is straightforward: if we use documented arguments, they should just work. Specifically, when transitioning from older methods like use_container_width (which is also being deprecated in favor of specifying dimensions within the configargument) to the newerwidth` argument, we expect it to function as described.

Expected Behavior: When using st.plotly_chart(fig, width="content"), the Plotly chart should render, taking up the width defined by its content. No deprecation warning related to kwargs should be displayed because width is a documented and supported parameter for this function. The intention is to leverage the width argument for specifying chart dimensions, aligning with modern API practices, and this should not be flagged as an unintended use of kwargs.

Current Behavior: As observed, the current behavior is that passing width="content" to st.plotly_chart does trigger a deprecation warning. The warning message specifically states: "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 is problematic because the user is not providing variable or arbitrary keyword arguments; they are using a parameter that appears to be documented and intended for use. The warning suggests that internally, width="content" is being processed in a way that the kwargs detection mechanism flags it, even though it’s a legitimate parameter.

This situation is frustrating because it creates noise in the development process. Developers might second-guess whether they are using the API correctly, even when they are following the documented instructions. It also raises concerns about the stability and predictability of the Streamlit API. If documented parameters trigger deprecation warnings, it can be difficult for users to know what is safe to use.

This issue is indeed a regression. It implies that in a previous version of Streamlit, using width="content" (or a similar string-based dimension specifier) did not trigger this specific kwargs deprecation warning. The introduction of the kwargs warning logic seems to have had an unintended side effect on how certain well-defined parameters are handled. The goal of refactoring APIs is usually to improve clarity and robustness, and in this case, it appears to have introduced a confusing side effect for users trying to leverage specific layout options.

Navigating the width and config Arguments

So, what's the best way forward when you encounter this warning? The warning itself gives us a strong hint: "Use the config argument instead to specify Plotly configuration options." This suggests that while width might be a direct parameter in some contexts, the more robust and future-proof way to handle Plotly-specific configurations, including dimensions, is through the config dictionary.

Let's revisit the reproducible code and see how we might adapt it to use the config argument. The config dictionary in st.plotly_chart is designed to pass Plotly.js configuration options directly to the chart.

Adapting the Code: Instead of passing width="content" as a direct argument to st.plotly_chart, you would include it within the config dictionary. For Plotly charts, options related to layout and sizing that were previously passed directly to st.plotly_chart can often be handled within the layout object of the Plotly figure itself, or through the config parameter for runtime behaviors and certain Plotly.js specific configurations.

However, for st.plotly_chart, the width and height parameters you pass directly to the st.plotly_chart function are Streamlit-specific arguments that control how the chart is rendered within the Streamlit app, not necessarily direct Plotly.js config options. The config argument in st.plotly_chart is primarily for Plotly.js configuration objects, which might include things like scrollZoom, displayModeBar, etc.

If the intention is to control the display width within Streamlit's layout, and width="content" is being flagged, the most direct Streamlit recommendation is often use_container_width=True. This tells Streamlit to make the chart expand to fill the width of its containing Streamlit element.

Let's clarify the roles:

  • fig.update_layout(width=..., height=...): This sets the intrinsic dimensions of the Plotly figure itself. Plotly will try to render the chart at these dimensions.
  • st.plotly_chart(fig, width=..., height=...): These are Streamlit arguments that control how the fig is embedded. width="content" is a special Streamlit value here.
  • st.plotly_chart(fig, use_container_width=True): This tells Streamlit to ignore the width and height set in fig.update_layout and instead make the chart responsive to the Streamlit container's width.
  • st.plotly_chart(fig, config={...}): This passes Plotly.js configuration options. It does not typically control the Streamlit embedding dimensions like width="content" or use_container_width=True. It's more for controlling Plotly's own UI elements and behaviors (like toolbars, zooming behavior, etc.).

Given the deprecation warning specifically mentioning kwargs and pointing to the config argument, it's possible that future versions of Streamlit intend for all display-related configurations, including responsive sizing, to be handled within config. However, as of the version mentioned (1.50.0), width and height are still listed as direct parameters for st.plotly_chart. If width="content" is causing the warning, and you want to avoid it while achieving a similar effect:

  1. Use use_container_width=True: This is the most direct Streamlit way to make charts responsive.

    st.plotly_chart(fig, use_container_width=True)

  2. Set explicit dimensions in fig.update_layout: If you don't need full responsiveness and just want a fixed size that might adapt slightly, ensure your fig.update_layout has sensible dimensions.

    fig.update_layout(width=500, height=360)
st.plotly_chart(fig) # No width argument needed here if fig has dimensions

The warning seems to indicate that the internal routing for width="content" is hitting the kwargs detection. The recommended fix from the warning is to use the config argument. However, config is typically for Plotly.js internal settings, not Streamlit's embedding dimensions. This points to a potential bug or an area where documentation might need clarification as Streamlit evolves.

For now, if width="content" is causing issues, relying on use_container_width=True is likely the most stable and supported alternative within Streamlit for achieving responsive chart sizing.

Conclusion: Embracing API Evolution

It's completely understandable to be puzzled when a documented feature like st.plotly_chart(fig, width="content") starts throwing deprecation warnings. These situations highlight the dynamic nature of software development, where APIs are constantly refined to improve usability, performance, and maintainability. The deprecation warning regarding kwargs is a signal from the Streamlit developers that they are moving towards a more structured way of handling parameters, aiming for greater clarity and reduced ambiguity.

While the current behavior might feel like a bug, it's more accurately described as an unintended consequence of an API refactor. The good news is that Streamlit provides clear guidance: use the config argument for Plotly-specific configurations. Even though the direct application of config to replace width="content" might not be immediately obvious (as config typically governs Plotly.js runtime options, not Streamlit's embedding dimensions), the principle remains sound – embrace the evolving API.

For users encountering this specific warning, the most practical workaround is often to utilize use_container_width=True when you want your Plotly charts to be responsive to the Streamlit container's width. This is a well-established Streamlit feature that achieves a similar goal without triggering the kwargs warning.

As Streamlit continues to develop, keeping an eye on their official documentation and release notes is crucial. Understanding these changes, even the ones that cause minor hiccups, helps us write more robust and future-proof Streamlit applications. The journey of API evolution is about making things better in the long run, and by adapting to these changes, we contribute to a more stable and powerful data visualization ecosystem.

If you're looking for more in-depth information on Streamlit's components and best practices, the official Streamlit Documentation is an invaluable resource. For deep dives into Plotly's charting capabilities, the Plotly Python Documentation is the place to go.