Streamlit: `plotly_chart` `kwargs` Deprecation With `width`
Many Streamlit developers are encountering a frustrating deprecation warning when using st.plotly_chart, specifically when trying to set the chart's dimensions with the width="content" parameter. It’s puzzling because width is a perfectly documented parameter, not some random keyword argument. This article will dive deep into why this kwargs deprecation warning appears, especially with width="content", and how you can effectively resolve it to keep your Streamlit applications clean, efficient, and free from annoying console messages. We'll explore the underlying changes in Streamlit's st.plotly_chart function, understand the concept of kwargs (keyword arguments), and provide practical solutions to ensure your Plotly charts display perfectly without triggering any warnings. Streamlit is an incredible tool for building interactive data applications with Python, allowing developers to create beautiful dashboards and visualizations with minimal code. Plotly charts are often at the heart of these applications, offering rich, interactive data representations. However, as frameworks evolve, so do their APIs. Deprecation warnings are a part of this evolution, signaling that certain ways of doing things will change or be removed in future versions. While these warnings are crucial for maintaining code health and adapting to new best practices, they can certainly be a head-scratcher when they appear for seemingly standard usage, such as setting chart width to "content". Our goal here is to demystify this particular warning, explain its technical roots, and guide you through the process of updating your code to align with Streamlit's latest recommendations, ensuring a smooth development experience. This isn't just about silencing a warning; it's about understanding the internal workings of st.plotly_chart and making your code more robust and future-proof.
Understanding the st.plotly_chart kwargs Deprecation Warning
The core issue at hand revolves around a rather specific yet common scenario: you’re using st.plotly_chart in your Streamlit application, attempting to define the chart's width (or even height) using a clear, documented parameter like width="content", and then, bam! — a deprecation warning pops up about kwargs. This warning 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." Now, if you’re like many developers, you’re probably scratching your head, thinking, "But I am using a documented parameter, width, not some arbitrary kwargs!" And you'd be right to feel that way. The confusion stems from how Streamlit internally processes these parameters. Historically, st.plotly_chart might have accepted a broader range of keyword arguments that were directly passed to Plotly's underlying configuration. However, as Streamlit refines its API for better maintainability and clarity, it's moving towards a more structured approach. The warning indicates that any keyword argument not explicitly defined as a direct parameter in the st.plotly_chart function signature is now considered a "variable keyword argument" (or kwargs) and is thus deprecated. This means that while width seems like a direct parameter, in the context of this deprecation, Streamlit is treating it differently, leading to this unexpected notification. The goal of this change is to streamline how Plotly configuration options are passed, centralizing them through a dedicated config argument. This makes the API more predictable and easier to manage in the long run. However, the immediate effect for developers is this slightly confusing warning, especially when using what appears to be a standard, explicitly supported option like width="content". The community has noted this, and it points to a nuanced aspect of API design where seemingly straightforward usage can still fall into a deprecated category due to internal argument handling. Understanding this distinction is key to fixing the warning and ensuring your Streamlit apps continue to run smoothly.
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")
What Exactly is kwargs and Why the Change?
To fully grasp why this st.plotly_chart deprecation warning is appearing, particularly when you use what seems like a perfectly valid parameter such as width="content", we first need to understand the concept of kwargs in Python and how APIs evolve. In Python, **kwargs (short for keyword arguments) is a powerful syntax that allows a function to accept an arbitrary number of keyword arguments. These arguments are then collected into a dictionary within the function, where keys are the argument names and values are their corresponding values. This flexibility is incredibly useful for functions that need to be highly adaptable or that act as wrappers for other functions, passing on unrecognized arguments. In the context of Streamlit’s st.plotly_chart, previous versions might have broadly accepted any keyword argument and passed it along to the underlying Plotly rendering mechanism. This offered a lot of convenience, as developers didn't have to worry about whether a specific Plotly configuration option was directly exposed as a Streamlit parameter. However, this convenience comes with a trade-off: it can make the API less explicit, harder to validate, and more challenging to maintain as the framework grows. Imagine trying to debug why a specific Plotly option isn't working if Streamlit is just blindly passing all kwargs through. It becomes a black box. Streamlit, as a mature and rapidly evolving framework, is moving towards a more explicit API design. This means clearly defining which parameters st.plotly_chart directly supports and funneling all other Plotly-specific configuration options through a dedicated, structured argument – the config dictionary. By doing this, Streamlit can better control and validate the inputs, provide clearer documentation, and reduce the likelihood of unexpected behavior. The deprecation warning you’re seeing is Streamlit's way of telling you, "Hey, this width parameter, while useful for layout, is no longer being treated as a direct st.plotly_chart parameter in the way it used to be. It's now falling into the kwargs bucket, and we want you to use the config argument for these types of settings moving forward." This shift is a common pattern in API development, aiming for a more robust and future-proof codebase, even if it introduces a temporary period of adjustment for developers.
The Problem: width="content" Triggering kwargs Warning
The heart of the frustration for many Streamlit users lies in the fact that width="content" (or even height with similar values) is a seemingly standard and well-documented parameter when working with st.plotly_chart. You’d expect it to be a first-class citizen, a parameter explicitly handled by Streamlit, rather than being caught in the generic kwargs net. Yet, that's precisely what's happening. When you pass width="content" to st.plotly_chart, Streamlit's internal logic, specifically the snippet mentioned in the issue description, if kwargs: show_deprecation_warning(...), triggers. This conditional check essentially says, "If there are any keyword arguments provided that aren't explicitly recognized by st.plotly_chart's official signature, then consider them kwargs and issue a warning." The crucial detail here is that width (with "content" or other specific values) is now not considered a direct, explicitly handled parameter within the st.plotly_chart function itself in the same way it might have been in earlier versions or how other arguments like use_container_width (which was also deprecated and replaced by width values like "container") are handled. Instead, it's being treated as an unrecognized keyword argument that would typically be passed down to Plotly's configuration options. This creates a confusing scenario where developers are trying to achieve responsive or specific sizing for their charts using what appears to be the recommended new API, only to be met with a deprecation notice intended for unstructured Plotly configuration options. The expected behavior was that by changing from the deprecated use_container_width to the width argument, as outlined in the documentation, users would not receive any deprecation warnings. The current behavior, however, is that width="content" does trigger the kwargs warning. This suggests a potential oversight in the implementation, where the width parameter (when set to "content" or "container") should perhaps be explicitly handled before the generic kwargs check, or it should be transformed internally into the config argument structure without explicitly telling the user to pass width directly via config. This discrepancy between the documented usage and the resulting warning is precisely why it feels like a regression. Developers are following the updated guidelines, yet still encountering warnings for what should be a straightforward use case.
Steps to Reproduce and Debugging Insights
To truly understand and troubleshoot this st.plotly_chart kwargs deprecation warning, it’s essential to be able to reliably reproduce the issue. Thankfully, the provided code example makes this straightforward, allowing any developer to experience the warning firsthand and contribute to finding a robust solution. The steps are quite simple: first, ensure you have Streamlit installed, preferably version 1.50.0 or later, as this is where the issue was specifically noted. Then, you just need to import plotly.graph_objects as go and streamlit as st. The core of the reproducible example involves creating a basic Plotly figure – in this case, a simple go.Barpolar chart. Crucially, the fig.update_layout call sets some initial width and height values, but the triggering action is in the final line: st.plotly_chart(fig, width="content"). When you run this Streamlit script (e.g., streamlit run your_script_name.py), you'll observe the application launch in your browser, displaying the Plotly chart. However, if you check your terminal or console where the Streamlit server is running, you'll immediately see the kwargs deprecation warning message. This confirms that even when using a seemingly valid and documented parameter like width="content", the internal kwargs check is being triggered. The debug information points to Streamlit version: 1.50.0, Python version: Python 3.14.2, Operating System: MacOs 26.1, and Browser: Chrome. This specific version information is invaluable for Streamlit maintainers and community members looking to diagnose the problem. It highlights that this is a recent development, likely introduced in version 1.50.0 or a very close predecessor, impacting a modern Python environment on a common operating system. The fact that this "used to work in a previous version" strongly suggests that it is indeed a regression, where a change intended to improve the API or fix another issue inadvertently introduced this unexpected warning for a seemingly correct usage pattern. Developers expect backward compatibility or clear migration paths, and in this case, the migration from use_container_width to width was not entirely smooth due to this kwargs conflict.
Solutions and Best Practices for plotly_chart
Navigating deprecation warnings is a common part of software development, and while the st.plotly_chart kwargs warning with width="content" can be a bit perplexing, there are clear strategies to address it and ensure your Streamlit applications remain clean and efficient. The most straightforward path forward, aligning with Streamlit's updated API design, is to leverage the config argument for any Plotly-specific settings that might trigger this warning. Remember, the deprecation message itself guides us: "Use the config argument instead to specify Plotly configuration options." For the width="content" scenario, this means we need to adjust how the sizing is passed. Instead of directly using width="content" as a parameter to st.plotly_chart, you would typically define a config dictionary that specifies how the chart should be rendered. However, it's crucial to note that width="content" is a Streamlit-specific instruction for responsive layout, not a direct Plotly config option in the traditional sense. This highlights the nuance of the problem: Streamlit's width parameter (which takes values like "container" or "content") should handle the sizing responsively, but it's currently falling into the kwargs bucket. The intended way to control embedding behavior for Plotly charts within Streamlit, beyond the figure's own layout, is usually through Streamlit's direct parameters. If width="content" is indeed being treated as kwargs, a temporary workaround might involve explicitly setting the width on the Plotly figure itself (e.g., fig.update_layout(width="auto") or a fixed pixel value) and avoiding the width="content" parameter in st.plotly_chart if the warning persists even with the most recent Streamlit versions that might address this bug. Another strategy, if you encounter the warning for other Plotly configuration options that st.plotly_chart doesn't explicitly expose, is to use the config dictionary. For example, to hide the Plotly mode bar, you'd pass config={'displayModeBar': False}. For the specific issue of width="content", the most ideal solution would be for Streamlit to explicitly handle this parameter internally, preventing it from being caught by the kwargs deprecation check. As of Streamlit 1.50.0, this seems to be an ongoing point of refinement. Developers should regularly update their Streamlit library to benefit from bug fixes and API improvements. Keeping your Python environment up-to-date (pip install --upgrade streamlit) is a fundamental best practice. Until a definitive fix is integrated, understanding that width="content" might still trigger the kwargs warning even though it seems like the right way to achieve responsive sizing post-use_container_width deprecation, means we might need to be a bit more creative or patient. For now, if the warning is intrusive and not yet resolved by an update, consider whether fig.update_layout(autosize=True, width=None, height=None) or similar Plotly-native responsive settings achieve your layout goal, allowing Streamlit to simply render the figure without additional width parameters that might trigger the warning.
Conclusion
Dealing with deprecation warnings can often feel like a hurdle, but they are vital signals from framework developers about evolving best practices and API improvements. The st.plotly_chart kwargs deprecation warning, particularly when triggered by width="content", highlights a specific area of refinement within Streamlit's API. While the intent is to streamline how Plotly configuration options are handled via the config argument, the immediate effect can be confusing for developers adhering to documented changes. We've explored the technical underpinnings, the specifics of the reproducible code, and the implications of this warning. By understanding the distinction between direct parameters and generic kwargs, you're better equipped to adapt your code. Keep an eye on Streamlit updates, as such issues are often addressed promptly in subsequent releases. For more insights into Streamlit and Plotly, refer to the official documentation and community resources.
