Fixing Plotly Chart Width Warning In Streamlit
Have you ever been busy building a fantastic Streamlit app, populating it with vibrant Plotly charts, and then BAM! A cryptic deprecation warning pops up? Specifically, you might have encountered something about "kwargs" when trying to set the width or height of your st.plotly_chart. It can be a bit perplexing, especially when you're just trying to make your charts look just right. Don't worry, you're not alone! This issue often arises when users try to utilize the width="content" (or similar string values) to dynamically adjust their charts' dimensions. It seems like a straightforward feature, but under the hood, Streamlit might be interpreting it in a way that triggers this warning, even if you haven't explicitly used variable keyword arguments. Let's dive deep into why this happens and how to navigate it smoothly. We'll break down the st.plotly_chart function, explore the deprecation warning, and provide a clear, actionable path forward. Understanding these nuances will help you build more robust and error-free Streamlit applications, ensuring your data visualizations shine without any unnecessary red flags.
The Mystery of the kwargs Warning in st.plotly_chart
The core of the issue lies in how Streamlit handles arguments passed to st.plotly_chart. When you use st.plotly_chart(fig, width="content"), you're telling Streamlit that you want the chart to take up the available width of its container. This is a super useful feature for making your dashboards responsive and good-looking on different screen sizes. However, the way this width parameter is processed internally has, in some versions of Streamlit, led to a deprecation warning related to kwargs. Specifically, the warning message might say 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 is a bit of a red herring in this context because you're not explicitly passing variable keyword arguments in your own code. You're using a documented parameter, width, with a documented value, "content". The deprecation warning is triggered because, behind the scenes, Streamlit might be forwarding this width argument in a manner that its internal logic flags as a potential use of kwargs that is being phased out. It’s like a polite, albeit sometimes confusing, heads-up that the underlying mechanism for handling certain types of arguments is changing. The developers of Streamlit are working to make the API cleaner and more predictable, and this warning is a sign of that ongoing effort. It's designed to guide users towards the more modern and recommended ways of configuring charts, which often involves using the config dictionary for Plotly-specific settings. While frustrating in the moment, this warning is ultimately intended to help developers maintain their applications as Streamlit evolves.
Why This Warning Appears (and Why It's Confusing)
The deprecation warning concerning kwargs in st.plotly_chart often surfaces when you attempt to control the chart's dimensions using parameters like width='content' or height='auto'. You might be thinking, "But I'm not using **kwargs myself! I'm just passing width='content' directly." And you'd be right! The confusion arises because Streamlit's internal handling of these arguments can sometimes trigger this warning. It's a consequence of Streamlit's internal architecture and how it forwards arguments to the underlying Plotly library. In essence, when you provide width='content', Streamlit might be passing this information along using a mechanism that, in newer versions, is being discouraged in favor of a more structured approach using the config parameter. The warning isn't necessarily saying you are misusing kwargs; rather, it's signaling that the way Streamlit is processing your input might involve mechanisms that are slated for removal. The developers are aiming to consolidate configuration options into the config dictionary, making it the single source of truth for customizing Plotly charts within Streamlit. This approach offers better clarity and maintainability. So, even though your code is functionally correct and achieves the desired visual outcome, the warning is a vestige of an older implementation detail. It's a way for Streamlit to say, "Hey, there's a newer, better way to do this, and the old way might not be around forever." To truly resolve this, you need to understand that the warning is less about your direct code and more about the internal plumbing Streamlit uses.
Reproducing the st.plotly_chart Warning: A Practical Example
To truly grasp this kwargs deprecation warning, let's walk through a simple, reproducible code example. This will help you see exactly when and how the warning appears, making it easier to troubleshoot in your own projects. Imagine you're creating a basic bar polar chart using Plotly and want to embed it into your Streamlit application.
Here's the Python code you might use:
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]))
fig.update_layout(width=500, height=360) # Setting layout dimensions
# Display the chart with dynamic width
st.plotly_chart(fig, width="content")
When you run this code in a Streamlit environment (especially with versions around 1.50.0 or similar where this warning became more prominent), you will likely see the deprecation warning in your console or Streamlit's output. The warning message, as mentioned before, will probably point to kwargs and suggest using the config argument instead. This is the crucial part: the warning appears despite you only using documented parameters (fig and width) and not explicitly passing any arbitrary keyword arguments (**kwargs). The width="content" is the specific trigger here. It's a valid and intended way to control chart responsiveness, yet it causes this internal flag to be raised. This makes it seem like you've done something wrong, when in reality, it's an artifact of Streamlit's internal argument handling. The good news is that recognizing this pattern is the first step to fixing it. By understanding that this specific use case is the culprit, you can then explore alternative ways to achieve the same visual result without triggering the warning.
The Code in Action: What You'll See
When you execute the provided Python script, Streamlit will render your bar polar chart. Visually, everything might look as expected – the chart should display correctly within its designated space. However, if you look closely at your terminal output or the Streamlit interface's developer console, you'll notice the accompanying deprecation warning. It's this warning that we're aiming to eliminate. The warning itself is informative, suggesting a move towards the config parameter for specifying Plotly configurations. While the width="content" functionality still works in terms of rendering the chart, the warning indicates that this method of control might be deprecated or less preferred in future versions. It's a signal from the Streamlit developers that they are refining how chart configurations are managed, pushing towards a more unified and explicit approach. This is common in software development as libraries evolve to become more robust and user-friendly over time. Recognizing this specific code snippet as the source of the warning is key to moving forward and applying the recommended solutions.
The Expected vs. Current Behavior: Bridging the Gap
Let's clarify what we anticipate versus what's actually happening. The expected behavior when transitioning from older methods of chart sizing to newer ones in Streamlit is that the process should be seamless and warning-free, provided you follow the documented guidelines. In this specific case, the documentation for st.plotly_chart suggests using parameters like width and height (or their string equivalents like `
