Streamlit Plotly Chart: Fixing Kwargs Deprecation Warnings

by Alex Johnson 59 views

Hey there, data visualization enthusiasts! If you've been working with Streamlit and its fantastic plotly_chart function, you might have stumbled upon a rather persistent deprecation warning. It pops up even when you're not intentionally using variable keyword arguments, which can be a bit confusing, right? Well, you're not alone! This article dives deep into this plotly_chart kwargs deprecation warning, explains why it happens, and how you can easily resolve it to keep your Streamlit apps running smoothly.

Understanding the plotly_chart Kwargs Deprecation Warning

Let's start by setting the stage. Streamlit's st.plotly_chart is a powerful tool for embedding interactive Plotly visualizations within your web applications. It's designed to be intuitive and flexible. However, with every software update, there are changes, and sometimes these changes introduce warnings to guide developers toward newer, more robust practices. The kwargs (keyword arguments) deprecation warning in st.plotly_chart is one such instance. Essentially, Streamlit is signaling that the way certain configurations are passed might be subject to change or removal in the future. The primary issue arises when you try to specify width or height using values like "content". While this is a documented and useful feature, it seems to trigger a warning that suggests you're misusing variable keyword arguments, even when you're not explicitly passing any. 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 can be perplexing because you’re simply trying to control the dimensions of your chart using a documented parameter. The code snippet provided in the original report shows a clear example: st.plotly_chart(fig, width="content") causes this warning to appear. This implies an internal logic within Streamlit that flags any non-standard or dynamic keyword arguments passed to the underlying Plotly functions, even if they are intended for direct use by Streamlit's charting component. The goal of this warning is to encourage users to consolidate all Plotly-specific configurations within the config dictionary, making the API cleaner and more predictable. However, in this specific case, it seems to be a bit overzealous, flagging a valid usage pattern. We'll explore how to navigate this and ensure your charts render without the unnecessary clutter of deprecation notices. This is crucial for maintaining clean code and ensuring your applications are future-proof.

The Root Cause: How Width and Height Trigger the Warning

So, why does setting width="content" or height="content" (or similar values) cause this kwargs deprecation warning in st.plotly_chart? The core of the issue lies in how Streamlit handles arguments passed to st.plotly_chart. Internally, Streamlit might be iterating through the keyword arguments provided and checking if they are meant for Plotly's configuration or for Streamlit's display. When you pass width="content", Streamlit interprets this as a directive for how the chart should be sized within the app's layout. However, the underlying mechanism that throws the deprecation warning might not be distinguishing between genuine, arbitrary kwargs and specific, documented parameters like width and height when they are used in certain ways. It appears that the warning is triggered by a general check for any kwargs that aren't part of a predefined, explicit whitelist or handled in a specific manner before being passed down to Plotly or its rendering engine. The introduction of the config parameter in Streamlit was intended to be the single source for all Plotly-specific settings. This includes things like displaylogo, scrollZoom, and potentially even dimensions if Plotly itself were to handle them dynamically. However, width and height as direct arguments to st.plotly_chart are Streamlit-specific controls for layout. The current implementation seems to have a slight mismatch where the warning logic isn't perfectly aligned with these Streamlit-specific layout parameters. It's like a security guard checking everyone for a specific badge, but sometimes flagging people who have a different, but equally valid, form of identification. The provided reproducible code example clearly demonstrates this. By simply adding st.plotly_chart(fig, width="content"), the warning surfaces. This suggests that the if kwargs: check in Streamlit's internal code is catching the width argument as if it were an arbitrary keyword argument being passed to Plotly, rather than a recognized Streamlit parameter for chart display. This is particularly relevant because width="content" is a helpful way to make charts adapt to the available space, and receiving a deprecation warning for it can be quite frustrating. We need a way for Streamlit to correctly identify and process these layout-related arguments without triggering the general kwargs deprecation notice. This problem essentially highlights a need for finer-grained argument handling within Streamlit's charting components to differentiate between framework-specific controls and deep Plotly configurations.

The Expected vs. Current Behavior

Let's clarify what we expect and what's actually happening. The expected behavior is straightforward: when you use st.plotly_chart and specify the width or height of your chart, perhaps using a value like "content" to make it responsive, you shouldn't receive any deprecation warnings. This is because width and height are documented parameters intended for controlling the chart's display within the Streamlit layout. The transition from the older use_container_width to the width argument was meant to streamline this, and users expect it to function without unintended side effects. The documentation suggests that using width and height directly is the correct way to manage these aspects.

On the other hand, the current behavior, as observed and reported, is that users are receiving a deprecation warning. Specifically, the warning message: "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." appears. This happens even when the user is only passing documented parameters like width="content" and is not attempting to pass any other arbitrary keyword arguments. The code st.plotly_chart(fig, width="content") is the culprit here. It seems that Streamlit's internal check for kwargs is too broad and mistakenly flags the width parameter as a deprecated variable keyword argument. This creates a confusing user experience, as the warning implies a misuse of the API that isn't actually occurring according to the documentation. This isn't just a minor annoyance; it can mask other, more genuine, deprecation warnings and makes it harder to maintain clean, professional-looking applications. The fact that this is flagged as a regression indicates that this behavior was not present in previous versions, further emphasizing that it's an unintended consequence of recent code changes.

Reproducible Code Example and Steps to Reproduce

To help illustrate the issue clearly, let's look at the provided reproducible code example:

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 is concise and directly demonstrates the problem. It imports the necessary libraries, creates a simple Plotly figure, and then attempts to display it using st.plotly_chart, specifying width="content". When you run this code in a Streamlit application (version 1.50.0 or similar, on Python 3.14.2 with macOS 26.1, though the OS and browser are less likely to be direct factors here), you will see the deprecation warning appear in your console or Streamlit app output.

The steps to reproduce are as simple as running the code above:

  1. Install necessary libraries: Ensure you have streamlit and plotly installed (pip install streamlit plotly).
  2. Create a Python file: Save the code snippet above into a Python file (e.g., app.py).
  3. Run the Streamlit app: Open your terminal, navigate to the directory where you saved the file, and run streamlit run app.py.
  4. Observe the output: When the app loads in your browser, you should see the Plotly chart, and accompanying it, the deprecation warning related to kwargs.

This straightforward reproduction path makes it easy for Streamlit developers to verify the issue and for the Streamlit team to debug and fix it. The problem isn't dependent on complex data or intricate plot configurations, but rather on the interaction between the width parameter and Streamlit's argument parsing logic.

The Solution: Leveraging the config Argument

While the warning might seem like a bug, Streamlit's intention behind it is to guide developers towards a more standardized way of passing Plotly configurations. The recommended approach, as hinted by the warning itself, is to utilize the config argument. Even though width and height seem like layout parameters for Streamlit, Plotly itself has a config object where various rendering options can be specified. To resolve the deprecation warning when using width="content" or similar responsive sizing, you can pass these parameters within the config dictionary.

Here’s how you can modify the code to resolve the warning:

import plotly.graph_objects as go
import streamlit as st

fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
# Remove width and height from update_layout if you want it to be fully responsive
# fig.update_layout(width=500, height=360)

# Pass width and height within the config dictionary
config = {
    "responsive": True, # Often helpful for "content" width/height
    "autosize": True,   # Another option that might be relevant
    "width": "content",  # Or use a specific pixel value if "content" is still an issue
    "height": "content"  # Or use a specific pixel value
}

st.plotly_chart(fig, config=config)

Explanation:

  • config Dictionary: We create a dictionary named config. This dictionary will hold all the Plotly-specific configurations.
  • responsive: True: This is often a good companion to responsive sizing. It tells Plotly to try and resize the chart when its container resizes.
  • autosize: True: Similar to responsive, this can help ensure the chart fits its container.
  • Passing width and height: Instead of passing width="content" directly as an argument to st.plotly_chart, we now include it inside the config dictionary. This tells Streamlit to pass these as Plotly configuration options.

By consolidating these parameters within the config dictionary, you are adhering to Streamlit's preferred method for passing Plotly configurations. This approach bypasses the specific check that flags arbitrary kwargs and effectively resolves the deprecation warning. It's a clean way to manage your chart's display properties and ensures your code remains compatible with future Streamlit updates. Remember to consult the Plotly documentation for a full list of available configuration options that can be passed via the config dictionary.

Conclusion: Embracing Streamlit's Evolving API

Dealing with deprecation warnings can sometimes feel like a nuisance, especially when they appear for seemingly valid uses of documented features. The plotly_chart kwargs deprecation warning when using width="content" is a prime example of this. However, these warnings are often Streamlit's way of nudging developers towards a more robust, standardized, and future-proof API. In this case, the solution lies in understanding that while width and height control the display, they can be effectively managed within Plotly's config object, which Streamlit exposes.

By passing your desired chart dimensions and other Plotly-specific settings within the config dictionary, you not only eliminate the confusing deprecation warning but also align your code with Streamlit's recommended practices. This proactive approach ensures that your applications remain stable and compatible as Streamlit continues to evolve. It’s a small change that brings significant clarity and peace of mind to your development workflow.

For further exploration into Streamlit's capabilities and best practices, you might find these resources helpful: