Fix Plotly Chart Width Bug

Hey there, fellow data enthusiasts! Ever found yourself wrestling with a pesky deprecation warning in Streamlit, even when you're sure you're doing things by the book? You're definitely not alone! Today, we're diving deep into a peculiar issue that's been popping up when using the st.plotly_chart function, specifically when trying to control the chart's width with the "content" setting. It seems like even when we're not explicitly passing any extra keyword arguments (kwargs), Streamlit is giving us a heads-up about their deprecation. This can be a bit confusing, especially when you're just trying to make your visualizations fit nicely within your app. Let's unravel this mystery together, understand why it's happening, and how you can navigate it smoothly to keep your Streamlit apps clean and warning-free. We'll explore the root cause of this unexpected warning and provide clear, actionable steps to ensure your Plotly charts display perfectly without any unnecessary alerts.

Understanding the `st.plotly_chart` and `kwargs`

So, what's the deal with kwargs, and why does it suddenly seem to be causing a stir with st.plotly_chart? In Python, **kwargs is a special syntax that allows a function to accept an arbitrary number of keyword arguments. Think of it as a flexible way to pass extra, named information to a function without having to define each parameter explicitly. For instance, if a function is defined as def my_function(**kwargs):, you could call it like my_function(name='Alice', age=30, city='New York'), and all these arguments would be collected into a dictionary named kwargs inside the function. It's a powerful tool for creating flexible and extensible code.

Now, in the context of Streamlit's st.plotly_chart function, the developers have been working on refining how parameters are handled. Specifically, they've been moving away from accepting certain arguments directly as kwargs and encouraging the use of a more structured approach, often through a config dictionary. This is a common practice in software development to make APIs clearer, more maintainable, and less prone to naming conflicts. When a function is updated to deprecate certain kwargs, it means that while the old way might still work for a while, it's flagged for future removal. The goal is to guide users towards the new, preferred method.

The crux of the current issue is that users are encountering this deprecation warning even when they are using documented parameters, like setting the width to "content". 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," is being triggered inappropriately. This suggests that the internal logic of st.plotly_chart might be interpreting some of its own internal argument handling as if a user had passed an unrecognized kwarg, or that the logic for checking for 'extra' kwargs is a bit too eager. It's like calling a friend and getting a warning about speaking too loudly, even when you're just saying "hello." This isn't ideal, as it can lead to confusion and make developers second-guess their own code, wondering if they've missed something obvious.

The intention behind deprecating direct kwargs for certain functionalities is usually to streamline the API. For st.plotly_chart, this might mean that parameters related to Plotly's underlying configuration should be passed within a dedicated config dictionary, rather than as top-level arguments to the Streamlit function. This keeps the Streamlit function's signature cleaner and separates Streamlit-specific controls (like use_container_width, which has itself been refactored) from Plotly-specific configurations. However, when this deprecation warning pops up for standard, documented usage, it indicates a mismatch between the warning's trigger and the actual user input, which is what we need to address.

The Specific Issue: `width="content"` and Unexpected Warnings

Let's zoom in on the specific scenario causing the stir: using st.plotly_chart(fig, width="content"). This is a perfectly valid and useful way to tell Streamlit to make your Plotly chart dynamically adjust its width to fill the available space in its container. It's a feature that many of us rely on to create responsive and good-looking dashboards. The problem arises because, upon running this code, users are greeted with a deprecation warning related to kwargs, even though width="content" is a documented parameter and they aren't passing any other arbitrary keyword arguments.

The warning message itself points towards using the config argument instead for Plotly options. This implies that Streamlit might be internally treating the width parameter, when set to "content", in a way that triggers its kwargs checking mechanism. It's possible that the function's internal code checks for any arguments that aren't explicitly defined in its signature and then passes them along to an underlying Plotly or Streamlit component. If the logic for identifying 'unknown' kwargs is too broad, it might incorrectly flag a known, documented parameter like width when used in a specific way.

A typical reproducible example that highlights this issue looks something like 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]))
fig.update_layout(width=500, height=360) # These are Plotly layout args
st.plotly_chart(fig, width="content") # This is the Streamlit arg causing the warning

When you run this simple script, you'll see your chart rendered correctly, but accompanied by the deprecation warning. This is frustrating because it introduces noise into your application's output, making it harder to spot genuine issues. It also raises questions about the stability of the component – if a documented feature triggers a deprecation warning, are there other hidden issues or upcoming breaking changes we should be aware of?

The expected behavior, naturally, is that using documented parameters like width="content" should not trigger warnings about deprecated kwargs. The developers of Streamlit have been diligent in providing clear documentation and migration paths for deprecated features. This warning, however, seems to be a case where the mechanism designed to warn about *unintended* or *misused* keyword arguments is being erroneously activated by a *correctly used* and *intended* parameter. This suggests a potential bug in how Streamlit's plotly_chart function parses and validates its arguments, particularly when dealing with dynamic width settings.

This issue can be considered a regression because, as reported, this behavior was not present in previous versions. Users expect that functionality which was working fine before should continue to work without new, unexpected warnings after an update. The fact that it used to work without this warning implies that a recent change in Streamlit's codebase has inadvertently introduced this behavior. Understanding the exact change that led to this requires delving into Streamlit's version history and commit logs, but for the end-user, the impact is a less-than-ideal developer experience.

Why is this Happening? Potential Causes and Solutions

Let's put on our detective hats and explore why this unexpected kwargs deprecation warning might be popping up when using width="content" with st.plotly_chart. The core of the issue likely lies in how Streamlit's internal argument handling logic intersects with the specific way the width parameter is processed. As mentioned, Streamlit is moving towards a more structured approach for passing configurations, often consolidating them into a config dictionary. When you use a parameter like width="content", Streamlit needs to interpret this instruction and apply it appropriately, likely by passing it down to the underlying charting library or its own rendering component.

One strong possibility is that the check for kwargs is being performed before all known, documented parameters have been fully processed or accounted for. If Streamlit's internal mechanism iterates through all provided arguments and flags anything that isn't in its primary list of expected parameters, it might be catching width in this net. The fix would involve ensuring that documented parameters like width, height, use_container_width (though this has been refactored), and potentially others are explicitly recognized and handled before the general kwargs check is made. The warning is intended for situations where a user might pass something like st.plotly_chart(fig, some_random_arg='value'), which Streamlit doesn't know how to handle directly and should instead be put into the config. The current bug seems to be mistaking a legitimate parameter for an unknown one.

Another angle to consider is how the width="content" value itself is interpreted. While it's a clear instruction to Streamlit, the internal code might be doing some processing or passing it in a way that looks like an arbitrary keyword argument to another part of the system. For example, if Streamlit's code passes this parameter down to a component that expects specific keyword arguments, and that component's interface changes or has its own argument handling that flags width unexpectedly, it could cascade into the warning we're seeing. The traceback from such an issue would be crucial here, as it would show exactly which function is issuing the warning and in what context.

The provided example code shows that the fig.update_layout(width=500, height=360) are arguments passed to the Plotly figure itself, controlling its internal layout. The problematic argument is width="content", which is passed to st.plotly_chart. This distinction is important: st.plotly_chart accepts its own set of arguments to control how the figure is displayed within the Streamlit app, separate from the arguments that configure the Plotly figure's appearance and data. The deprecation warning seems to be incorrectly triggered by Streamlit's handling of its own display parameters.

The fix, from a user's perspective, often involves waiting for a Streamlit update that addresses this specific bug. However, if you're encountering this in a development environment and need a workaround, you might consider:

• Explicitly setting `use_container_width=True`: If your goal is simply to have the chart fill the container, and the "content" value was a way to achieve this, try using use_container_width=True instead. This parameter has been the standard way to achieve full-width charts in Streamlit for some time and might bypass the specific logic triggering the kwargs warning.
• Using a fixed pixel width: If dynamic width isn't strictly necessary, you could use a fixed pixel value for the width argument (e.g., width=700) or rely on the default behavior. This avoids using the "content" string which seems to be the trigger.
• Checking Streamlit Updates: Keep an eye on the Streamlit release notes. Issues like this are often fixed in subsequent patches or minor releases. Updating to the latest version is usually the best long-term solution.

The underlying fix within Streamlit would involve refining the argument parsing logic in the st.plotly_chart function. It needs to correctly identify and process all its documented parameters, including special string values for width/height, before flagging any remaining arguments as potentially problematic kwargs. This ensures that users receive helpful warnings only when they are actually using the function in an unintended or deprecated manner, leading to a cleaner and more intuitive development experience.

Is This a Regression? And What to Do Next

The question of whether this is a regression is a crucial one for understanding the impact and urgency of the issue. Based on the information provided, yes, this is very likely a regression. A regression occurs when a feature that previously worked correctly stops working in a newer version of the software, or when a new, unexpected behavior is introduced that disrupts existing functionality. If users were previously able to use st.plotly_chart(fig, width="content") without receiving any deprecation warnings, and now they are, it clearly indicates that a change in a recent Streamlit update has caused this undesirable side effect. This is particularly frustrating as it affects code that was considered standard and correct.

Regressions can happen for various reasons. Developers might refactor internal code to improve performance or maintainability, and in doing so, inadvertently alter the behavior of existing features. They might update underlying libraries, which could have different ways of handling parameters, leading to unforeseen conflicts. Or, as suspected in this case, a new warning mechanism might be implemented with logic that is slightly too broad, catching legitimate use cases along with problematic ones. Regardless of the cause, the impact on the user is a broken or less reliable experience.

So, what should you do if you encounter this regression?

1. Verify the Issue: First, double-check that you are indeed using documented parameters and that no other unexpected arguments are being passed. Run the provided minimal reproducible example to confirm the behavior.
2. Check for Updates: As mentioned earlier, Streamlit is actively developed. Visit the official Streamlit GitHub repository or PyPI page to see if a newer version has been released that specifically addresses this known issue. Often, bugs like this are quickly identified and fixed.
3. Use Workarounds (If Necessary): If an immediate fix isn't available, consider the workarounds discussed previously. Using use_container_width=True is often a good substitute if the goal is simply to make the chart responsive. Alternatively, using a fixed pixel width can bypass the problem altogether, though it sacrifices responsiveness.
4. Report the Issue (If Not Already Done): The initial report seems to have been made on a platform like GitHub issues. If you are experiencing this, it's beneficial to add your experience (e.g., your Streamlit version, Python version, OS) to the existing issue. This helps developers gauge the impact and prioritize the fix. If you can't find an existing issue, creating a new one with a clear, reproducible example is essential.
5. Provide Debug Information: When reporting or discussing the issue, including the debug information requested by Streamlit (version numbers, OS, browser, etc.) is vital. This helps developers pinpoint the exact environment where the bug occurs. The provided debug info in the original report (Streamlit 1.50.0, Python 3.14.2, macOS 26.1, Chrome) gives a good starting point.

By actively participating in the Streamlit community – whether by reporting bugs, suggesting solutions, or confirming existing issues – you help ensure that the library remains robust and user-friendly for everyone. Addressing regressions promptly is key to maintaining developer trust and satisfaction. The goal is to have a development environment where you can focus on building great applications, not on deciphering confusing warnings.

It's always a good practice to keep your dependencies updated, but also to be aware of potential breaking changes or new behaviors introduced in updates. Reading release notes can save a lot of troubleshooting time. For those using Streamlit for data visualization, ensuring that components like st.plotly_chart function as expected is paramount. A clean output without spurious warnings contributes significantly to the maintainability and readability of your Streamlit applications.

Conclusion: Towards Cleaner Streamlit Visualizations

Navigating the nuances of software updates can sometimes feel like a puzzle, and the kwargs deprecation warning with st.plotly_chart when using width="content" is a prime example. While the intention behind such warnings is to guide developers towards more robust and future-proof coding practices, it's essential that these warnings are triggered accurately. The current situation, where a documented and functional parameter seems to illicit an inappropriate warning, points to a small but noticeable friction in the user experience.

We've explored the role of kwargs in Python, understood how Streamlit aims to manage parameters for its components, and pinpointed the specific scenario causing the unexpected warning. The good news is that this appears to be a regression, likely stemming from an overly broad argument-checking mechanism within Streamlit's internal code. Developers are actively working on such libraries, and issues like this are typically high on the priority list for resolution in upcoming releases.

For now, the best course of action is to stay informed by checking for Streamlit updates, utilizing documented workarounds like use_container_width=True if applicable, and contributing to the issue tracker if you encounter this. By providing clear, reproducible examples and debugging information, you empower the Streamlit team to fix these issues efficiently. Ultimately, the goal is to achieve a seamless experience where you can focus on the creative aspects of data visualization and application building, rather than getting sidetracked by misleading warnings.

Let's continue to build amazing data applications with Streamlit! For more insights into Streamlit best practices and advanced techniques, I highly recommend checking out the official **Streamlit Documentation**. Additionally, the **Plotly Python documentation** is an invaluable resource for mastering your visualizations.