Streamlit Plotly Chart: Fixing `kwargs` Deprecation Warnings

by Alex Johnson 61 views

Hey there, data enthusiasts! Ever run into that pesky deprecation warning when using st.plotly_chart in Streamlit, especially when trying to set the width or height? You know, the one that talks about variable keyword arguments (kwargs) being deprecated, even when you're pretty sure you haven't passed any extra, undocumented arguments? Well, you're not alone! It seems like a common hiccup that can throw a wrench in your otherwise smooth Streamlit development workflow. Let's dive deep into why this happens and, more importantly, how to get around it so your code runs clean and warnings-free.

Understanding the kwargs Deprecation Warning in Streamlit

First off, let's talk about what this kwargs deprecation warning actually means. In Python, **kwargs is a special syntax that allows a function to accept an arbitrary number of keyword arguments. When you see a warning about kwargs being deprecated in st.plotly_chart, it's generally signaling that the way Streamlit used to handle certain configurations, possibly through these flexible keyword arguments, is changing. The developers are encouraging a more structured approach, typically by using a dedicated config argument for Plotly-specific settings. This makes the function signatures clearer and reduces the chance of unexpected behavior. The issue arises because, even when you're using documented parameters like width='content' or height=500, Streamlit's internal handling might still be triggering this warning. It's a bit like your car dashboard flashing a warning light for a system you're not actively using – confusing and a little annoying!

The core of the problem, as described in the original issue, is that the warning is being triggered even when only documented parameters are used. For instance, setting st.plotly_chart(fig, width='content') should be a perfectly valid operation according to the documentation. However, the warning appears because the internal code is checking for the presence of kwargs and, in this specific scenario, seems to be incorrectly flagging the use of the width parameter as if it were an arbitrary, undocumented keyword argument. This is a classic case of a warning being a bit too eager, or perhaps a slight mismatch between the internal implementation and the user-facing documentation or expectations. The intent behind the deprecation is good – to make the API cleaner and more predictable. But when it flags legitimate usage, it can be a roadblock.

This situation is particularly frustrating because it can obscure actual deprecation warnings or unintended uses of keyword arguments. If your console is flooded with warnings about kwargs when you're just trying to adjust your chart's display, it becomes harder to spot other important messages. The goal of Streamlit is to make app development easy and intuitive, and receiving these kinds of warnings for standard operations goes against that principle. It's a small bug, but it impacts the developer experience, which is crucial for any framework.

Why width='content' Triggers the Warning

So, why does a seemingly straightforward parameter like width='content' set off this kwargs alarm? Let's peek under the hood. When Streamlit's st.plotly_chart function is called, it likely goes through a process where it checks the arguments it receives. The width and height parameters are meant to control the dimensions of the displayed Plotly chart. In Streamlit version 1.50.0 (as per the debug info), there was a change related to how keyword arguments were handled, possibly to enforce the use of the config dictionary for Plotly's internal settings. The code snippet provided shows a check: if kwargs: show_deprecation_warning(...). This condition is designed to catch any extra keyword arguments passed to the function that aren't explicitly defined parameters. However, it seems that in some versions or under certain conditions, the width or height parameters, when passed directly to st.plotly_chart (rather than through the update_layout of the Plotly figure itself, or perhaps through a specific config parameter), are being caught by this kwargs check. This suggests that width and height might have been reclassified internally, or the check is a bit too broad, encompassing parameters that are indeed intended for direct use with st.plotly_chart.

Think of it this way: the function signature might look something like st.plotly_chart(figure, ..., **kwargs). The developers intend for kwargs to be for things not otherwise specified. But if width and height are handled in a way that makes them appear as part of kwargs to the warning checker, even if they are documented parameters for st.plotly_chart itself, the warning will trigger. The example code st.plotly_chart(fig, width='content') explicitly passes width as a keyword argument. While width='content' is a documented way to control the chart's width, the internal logic might be treating all arguments passed after the figure object as potential kwargs that need scrutiny. The expected behavior is that documented parameters, including width and height when used with st.plotly_chart, should not trigger a deprecation warning related to undocumented keyword arguments. The current behavior, however, shows that this is not the case, indicating a regression or a bug in the warning mechanism itself.

This kind of issue often pops up during API refactoring. When parameters are moved around or their handling is changed, it's easy for older checks to become overzealous. The goal is to guide users towards the new, preferred way of doing things (like using the config argument for Plotly-specific options), but it’s important that this guidance doesn't create noise for users following the current, documented practices. The width='content' usage is a prime example where the warning is misplaced, making it seem like the user is doing something wrong when they are actually using the API as intended.

Reproducing the Issue: A Simple Example

Let's walk through the code example provided, which perfectly illustrates the problem. To see this warning in action, you'll need Streamlit version 1.50.0 or a similar version where this behavior is present.

First, ensure you have the necessary libraries installed:

pip install streamlit plotly

Then, create a Python file (e.g., app.py) with the following code:

import plotly.graph_objects as go
import streamlit as st

# Create a simple Plotly figure
fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))

# Update layout (though this is less relevant to the warning itself)
fig.update_layout(width=500, height=360)

# Display the chart using st.plotly_chart with width='content'
st.plotly_chart(fig, width='content')

Now, run this Streamlit app from your terminal:

streamlit run app.py

When the app loads in your browser, you should observe a deprecation warning in your terminal output (or potentially in the Streamlit app's developer console, depending on your setup). The warning will likely state something like: "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 appears despite width='content' being a documented and valid argument for controlling the chart's display size directly within st.plotly_chart. It's not an undocumented kwargs being passed; it's a standard parameter that's mistakenly triggering the warning.

This reproducible example is key because it isolates the issue. We're not passing any other unusual arguments. We're creating a standard Plotly figure and then telling Streamlit to render it, specifying a common dimension control. The fact that this triggers the kwargs warning is the bug. It highlights that the warning mechanism isn't correctly distinguishing between arbitrary, unhandled keyword arguments and the intended, documented parameters for controlling the st.plotly_chart component itself. The update_layout calls within the Plotly figure object are for configuring the figure before it's passed to Streamlit. The width='content' is an argument to st.plotly_chart, intended to control how Streamlit renders that figure. The warning suggests that Streamlit is interpreting this width argument in a way that invokes the deprecated kwargs handling path.

The Expected vs. Current Behavior: Clarity Needed

Let's be crystal clear about what we expect and what we're currently getting. The expected behavior when using st.plotly_chart with documented parameters, such as specifying width='content' or a numerical height, is that the chart should render correctly without any deprecation warnings related to kwargs. The documentation for Streamlit's st.plotly_chart should be our guide, and if it lists width and height as valid arguments for controlling the display, then using them should be a clean operation. This is especially true when migrating from older patterns, like use_container_width, to the newer, recommended width argument. Users should be able to make these documented changes without being spammed by warnings that suggest they are misusing the API.

On the other hand, the current behavior, as demonstrated by the reproducible code, is that passing width='content' to st.plotly_chart does trigger a deprecation warning concerning variable keyword arguments (kwargs). This warning implies that an unrecognized or non-standard argument has been passed, which is precisely what isn't happening. The warning is misleading because it flags a documented feature as if it were an error or an outdated practice. This is a clear indication of a regression – a feature that previously worked without issue now behaves unexpectedly, generating unnecessary warnings.

This discrepancy is important for a few reasons. Firstly, it erodes confidence in the stability and clarity of the Streamlit API. Developers rely on documentation and expect warnings to accurately reflect problematic code. Secondly, it can create noise, making it harder to spot genuine issues. If every use of width or height throws a kwargs warning, developers might start ignoring all warnings, potentially missing critical updates or error messages. The intended shift towards using the config argument for Plotly-specific Plotly configurations (like scrollZoom, displayModeBar, etc.) is a valid one, but it shouldn't invalidate or warn about the direct width and height arguments provided by Streamlit for controlling the component's rendering.

Essentially, the current behavior indicates a bug in the warning system itself. It's incorrectly categorizing a standard parameter (width) as an arbitrary kwarg that is subject to deprecation. The expected behavior is a seamless integration where documented parameters function as described without generating misleading warnings. This regression means that users updating Streamlit might encounter this issue, causing confusion and potentially requiring them to suppress warnings or seek workarounds.

Navigating the kwargs Warning: Solutions and Workarounds

While we wait for the Streamlit team to address this specific kwargs warning regression, there are a couple of ways you can manage or work around it. The most direct solution, if you're not actively using other arbitrary kwargs, is to suppress the warning for this specific function call. However, this is generally not recommended as a long-term fix, as it can hide other important warnings. A better approach involves understanding how Streamlit is processing the arguments and adjusting your code accordingly, if possible.

One potential workaround is to ensure that all Plotly-specific configurations are passed via the config argument, and that width and height are only passed as arguments to st.plotly_chart if they are explicitly documented and supported there. Looking at the code, the warning fires if kwargs:. This implies that if no other keyword arguments are passed, perhaps the warning won't trigger. However, the example st.plotly_chart(fig, width='content') does pass width as a keyword argument. If the width parameter is somehow being bundled into a general kwargs dictionary that the warning check sees before it's processed as a specific width argument, that would explain it.

For now, the most pragmatic approach if you're encountering this specific, non-problematic warning is often to ignore it if you're confident your usage is correct and documented. However, this isn't ideal. A more robust, though perhaps more verbose, solution might be to manage the figure's layout within the Plotly figure object itself, rather than passing width and height directly to st.plotly_chart. For example, you could try:

import plotly.graph_objects as go
import streamlit as st

fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))

# Set dimensions directly in the figure layout
fig.update_layout(width=500, height=360, autosize=True)

# Use st.plotly_chart without width/height arguments
st.plotly_chart(fig)

This approach relies on Plotly's own layout settings to dictate the size. However, this might not always give you the desired behavior of having the chart fill its container (width='content'). The width='content' parameter in st.plotly_chart is specifically designed for Streamlit's layout management, allowing the chart to adapt to the available space. If this is a critical feature for your app, reverting to an older version of Streamlit where this warning didn't occur might be a temporary solution, although not recommended for production.

The best long-term solution is for the Streamlit maintainers to refine the warning logic. They need to ensure that documented parameters passed directly to st.plotly_chart, like width and height, are not misinterpreted as arbitrary kwargs that trigger a deprecation notice. By accurately identifying what constitutes a true kwargs issue versus standard parameter usage, the developer experience can be significantly improved. Until then, carefully check if your usage aligns with current documentation and consider if Plotly's internal layout settings can achieve your goals if direct st.plotly_chart arguments are causing issues.

Conclusion: Towards Cleaner Streamlit Development

Experiencing deprecation warnings, especially when they seem misplaced, can be a jarring part of the development process. The kwargs warning in st.plotly_chart when using parameters like width='content' is a prime example of this. It highlights a small but significant friction point where the framework's intent to guide developers towards cleaner APIs inadvertently causes confusion for users following documented practices. While the underlying cause is likely a nuance in how Streamlit's internal argument parsing interacts with its warning system, the effect is a misleading message that can obscure real issues and detract from a smooth development experience.

We've explored why this happens – essentially, the warning mechanism is too broad and catches legitimate width and height arguments as if they were unhandled kwargs. The ideal scenario, our expected behavior, is for these documented parameters to function without triggering such warnings. The current behavior is the reality we're facing: unnecessary noise in our logs. While workarounds exist, such as adjusting how you define figure dimensions or, regrettably, ignoring the warning, the ultimate fix lies in refining Streamlit's internal logic to accurately differentiate between true kwargs misuse and standard API usage.

Streamlit's commitment to improving the developer experience means that issues like these are usually on the radar. By reporting them and providing clear, reproducible examples, the community helps the maintainers pinpoint and resolve these quirks. For now, understanding the root cause helps us navigate these small bumps. Remember, the goal is always to build amazing applications efficiently, and clear, accurate feedback from our tools is essential for that.

If you're interested in learning more about Plotly and Streamlit integrations, or deepening your understanding of interactive data visualization, check out these resources: