Fixing Plotly Chart Width Warning In Streamlit

by Alex Johnson 47 views

Hey there, fellow Streamlit enthusiasts! Ever been happily building your interactive dashboards, only to be greeted by a cryptic kwargs deprecation warning when using st.plotly_chart with specific width or height settings? Yeah, we've all been there. It's a bit like finding an unexpected note in your lunchbox – sometimes it's a surprise, but usually, it just makes you scratch your head. This little hiccup pops up even when you're not explicitly messing with variable keyword arguments, which can be super confusing. Today, we're going to dive deep into this issue, understand why it's happening, and most importantly, how to smoothly navigate past it to keep your Streamlit apps looking clean and professional.

Understanding the "kwargs Deprecation Warning"

The core of the problem lies in how Streamlit handles arguments passed to st.plotly_chart. When you use arguments like width='content' or height='content', you're essentially telling Streamlit to dynamically adjust the size of your Plotly chart based on its container. This is a fantastic feature, allowing your visualizations to be responsive and look great on different screen sizes. However, recent updates in Streamlit have aimed to streamline how arguments are handled, particularly with the introduction of a dedicated config argument for Plotly-specific settings. This push for cleaner argument management has inadvertently caused a warning to trigger when these size arguments are used.

Specifically, a piece of code was introduced that checks if any kwargs (keyword arguments) are present. If kwargs is not empty, it issues a deprecation warning, suggesting users move to the config argument for Plotly configurations. The issue arises because arguments like width and height, when not explicitly defined in the function signature in the way Streamlit expects for these specific use cases, might be caught by this kwargs check. This means you get a warning about variable keyword arguments being deprecated, even though you're using documented, specific arguments like width='content' and aren't passing in any arbitrary, unexpected keyword arguments.

It's important to distinguish between explicitly passing **kwargs in your Python code and having a function internally interpret certain arguments as part of a general keyword argument pool. The warning is designed to catch the former, but it’s currently being triggered by the latter in this specific scenario. This can be particularly frustrating because it doesn't indicate a mistake in your code but rather a slight mismatch in how Streamlit's internal argument handling is interacting with the Plotly chart component.

This situation highlights a common challenge in software development: maintaining backward compatibility while introducing new features and improving code structure. The Streamlit team is constantly working to enhance the library, and sometimes these improvements can lead to unintended consequences that affect user workflows. The goal is always to provide a better, more intuitive experience, but the path there can sometimes involve a few bumps in the road.

Why does this matter? A deprecation warning, even if it doesn't break your app's functionality, can clutter your console output, making it harder to spot genuine errors. It also signals that a change is coming, and while you might not need to act immediately, it's good practice to understand and address these warnings to ensure your application remains robust and up-to-date in the future. For developers focused on delivering a polished user experience, seeing these warnings can be a nagging distraction, prompting a desire for a cleaner, warning-free output.

Let's look at the code example that triggers this.

Reproducible Code Example and Steps to Reproduce

To really see this in action, let's break down the provided code snippet. It’s a straightforward example, making the appearance of the warning even more perplexing.

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")

This code does the following:

  1. Imports necessary libraries: plotly.graph_objects for creating the plot and streamlit for the web application framework.
  2. Creates a Plotly figure: An empty go.Figure() is initialized.
  3. Adds a trace: A Barpolar trace is added. While this specific trace and its arguments (r, theta, width) aren't the direct cause of the Streamlit warning, they create a valid Plotly figure that we want to display.
  4. Updates layout: The figure's layout is given explicit width and height values (500 and 360 pixels, respectively). These are standard Plotly layout parameters.
  5. Displays the chart with st.plotly_chart: Here's the crucial line: st.plotly_chart(fig, width="content"). This tells Streamlit to render the fig object and, importantly, to set the width of the chart container to 'content'. This is intended to make the chart responsive, adapting its width to fill its containing element.

The Problem: When you run this code in Streamlit, you'll see your beautiful barpolar chart rendered correctly. However, in your Streamlit terminal or logs, you'll likely find a warning message similar to this:

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.

Why is this happening? As discussed, the warning is triggered because Streamlit's internal logic for handling st.plotly_chart parameters is catching width='content' as part of a general keyword argument pool that it believes should be managed via the config parameter. It's not that you've done anything wrong in your usage of Plotly or Streamlit in terms of the direct parameters you're passing to the chart itself. The warning is a consequence of how Streamlit's plotly_chart function is structured and how it interprets arguments related to sizing and configuration.

The Expected Behavior vs. Current Behavior

The documentation for st.plotly_chart implies that arguments like width and height should be supported for controlling the display of the chart. When you use width='content', you're following the documented way to achieve responsive sizing. The expected behavior is that this should work seamlessly without any deprecation warnings. You're using a documented feature as intended.

The current behavior, however, is that this documented usage triggers the kwargs deprecation warning. This is because the internal implementation of st.plotly_chart is checking for unexpected keyword arguments, and width='content' is being flagged, possibly because it's not explicitly handled as a top-level argument in the same way other arguments might be, or because the warning logic is a bit too broad.

Is this a regression?

The issue states: Yes, this used to work in a previous version. This is a key piece of information. It means that in an older version of Streamlit, using st.plotly_chart(fig, width='content') did not produce this warning. This confirms it's a regression – a change in behavior introduced in a newer version that breaks or alters previous functionality. This is often caused by refactoring or updates to argument parsing within the Streamlit library itself.

Understanding these details is crucial for debugging and for providing clear feedback to the Streamlit development team. It pinpoints the exact functionality that's causing the issue and confirms it's not a user error but rather a change in the library's behavior.

Debugging and Potential Solutions

When faced with a regression like this, the first step is always to understand the context. We've established that the warning appears when using width='content' (or potentially height='content') with st.plotly_chart. The warning message itself points towards using the config argument for Plotly configuration options. Let's explore how we might apply this advice, even if it seems indirect.

Understanding the config Argument:

The config argument in st.plotly_chart is designed to pass Plotly.js configurations directly. This includes things like display modes, responsiveness settings, and other Plotly-specific behaviors. The warning suggests that size-related or other Plotly-specific configurations should be managed through this config dictionary.

Attempting a Solution with config:

While width='content' is a Streamlit-specific directive for responsiveness, Plotly itself has a config option for making charts responsive: responsive: True. Let's see if we can achieve the same effect and perhaps appease the warning by using this.

import plotly.graph_objects as go
import streamlit as st

fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
# It's generally better to set layout dimensions within the figure itself
# fig.update_layout(width=500, height=360) # These might be overridden by responsive settings

# Try passing responsive settings via the config argument
st.plotly_chart(fig, config={
 "responsive": True
})

In this revised code:

  • We've removed the explicit width and height arguments from st.plotly_chart.
  • We've introduced the config argument, passing it a dictionary {"responsive": True}. This tells Plotly.js to make the chart responsive to its container's size.

Why this might work:

  1. Addresses the warning directly: By using the config argument as suggested by the warning, you're telling Streamlit exactly where to put Plotly configurations. This bypasses the generic kwargs check that was causing the issue.
  2. Achieves responsiveness: "responsive": True in Plotly's config is the standard way to make charts adapt to their parent element's size. This should provide a similar visual outcome to width='content'.

Important Considerations:

  • width='content' vs. "responsive": True: While both aim for responsiveness, width='content' is a Streamlit-level control, whereas "responsive": True is a Plotly.js setting. They might have subtle differences in behavior or precedence. However, for most use cases, "responsive": True is the intended way to handle chart responsiveness within Plotly.
  • Layout dimensions: When using "responsive": True, the width and height parameters set directly in fig.update_layout() might behave differently. They might act as initial or minimum/maximum dimensions rather than fixed ones. It's often best to rely on the config for dynamic sizing when responsiveness is the primary goal.
  • Other kwargs: If you were previously using other keyword arguments with st.plotly_chart that are not related to Plotly configuration (e.g., custom Streamlit arguments that might have existed in older versions), you would need to find their modern equivalents or integrate them into the config dictionary if they are indeed Plotly-related.

Alternative (Less Ideal) Workaround:

If the config solution doesn't perfectly match your needs or if you're in a bind, another, less recommended, approach is to simply ignore the warning. This is generally not a good long-term strategy, as deprecated features are eventually removed. However, for immediate fixes or if the warning doesn't impact functionality, it's an option. You'd simply continue using width='content' and accept the warning until a more permanent fix is available or implemented.

The best course of action is to adapt to the recommended config parameter. It aligns with Streamlit's development direction and ensures your code is future-proof.

The Future of st.plotly_chart Arguments

Streamlit's evolution, like any active open-source project, involves continuous refinement. The move to deprecate kwargs for specific configurations and encourage the use of the config argument is a sign of this maturation. It aims to bring clarity and a more structured approach to passing Plotly-specific options.

  • Increased Clarity: By consolidating Plotly settings within the config dictionary, it becomes immediately obvious which parameters are for Plotly itself and which are for Streamlit's rendering. This reduces ambiguity and makes your code easier to understand for others (and your future self!).
  • Maintainability: As Plotly evolves, its configuration options change. Having a dedicated config argument allows Streamlit to remain compatible with a wider range of Plotly versions and features without needing to update the core st.plotly_chart function signature for every minor Plotly update.
  • Consistency: This approach aligns with how other components in Streamlit might handle complex configurations – through dedicated parameter objects or dictionaries. It promotes a consistent development pattern across the library.

What does this mean for developers?

It means we should all get comfortable with using the config dictionary for Plotly-related settings. This includes:

  • Responsiveness: As we've seen, {"responsive": True} is the way to go.
  • Mode Bar: Customizing the Plotly mode bar (the icons that appear on hover) is done through config. For example, {"displaylogo": False} to hide the Plotly logo.
  • Other Plotly behaviors: Any other Plotly.js configuration options can typically be passed here.

It's always a good idea to check the official Streamlit documentation for the most up-to-date information on argument handling. They often provide clear examples of how to use parameters like config effectively.

While the deprecation warning for width='content' might seem like a minor annoyance, it's a signal from the Streamlit team to adapt to a more robust and organized way of interacting with Plotly charts. Embracing the config argument will not only resolve the warning but also make your Streamlit applications more maintainable and aligned with the library's future direction.

In conclusion, the kwargs deprecation warning when using width='content' in st.plotly_chart is a current quirk in Streamlit's argument handling. The recommended solution is to switch to using the config argument with Plotly's built-in responsive settings ("responsive": True). This not only resolves the warning but also adheres to Streamlit's best practices for managing Plotly configurations, ensuring your applications are clean, efficient, and future-ready.

For more in-depth information on Plotly configurations and Streamlit integrations, I highly recommend checking out the official resources: