Fixing `plotly_chart` Kwargs Deprecation In Streamlit

Hey there, Streamlit developers and data enthusiasts! If you’ve been working with Streamlit for your data applications, especially when integrating stunning visualizations with Plotly, you might have recently encountered a rather puzzling warning: a plotly_chart kwargs deprecation warning. This particular warning can be a bit tricky, as it sometimes pops up even when you feel like you’re doing everything right, using documented parameters like width="content". Don't sweat it, though! We’re here to unpack this issue, understand why it's happening, and guide you through the process of resolving it so you can get back to building beautiful, interactive data apps without any annoying yellow banners.

Streamlit is celebrated for its simplicity and speed in turning Python scripts into shareable web applications. A core part of its appeal is how easily it lets you embed complex visualizations from libraries like Plotly. The st.plotly_chart function is your go-to for this, enabling you to display plotly.graph_objects figures directly in your app. However, as with any evolving software, APIs get refined, improved, and sometimes, features are deprecated. Deprecation means that a feature is still functional for now but is slated for removal in future versions, and developers are encouraged to switch to newer, often better, alternatives. The plotly_chart kwargs deprecation warning is a prime example of such an evolution, aimed at streamlining how you pass configuration options to Plotly charts within Streamlit.

The essence of the problem lies in how st.plotly_chart handles additional keyword arguments (**kwargs). In Python, **kwargs allows a function to accept an arbitrary number of keyword arguments. Historically, st.plotly_chart might have used this to pass various Plotly configuration options directly. However, the Streamlit team decided to introduce a dedicated config argument to make this process clearer and more explicit, aligning with best practices for API design. This change is generally a good thing, leading to more robust and readable code. The warning itself serves as a heads-up, guiding you towards this new, preferred method. But what happens when you're just using a seemingly standard parameter like width="content" and still get the warning? That’s where the confusion starts, and where we’ll dive deeper to uncover the root cause and provide clear solutions. Understanding this specific scenario is crucial because it highlights a nuanced interaction between intended API changes and how parameters are internally processed, making it appear as a regression for users who are merely following the updated documentation. Our goal is to make your Streamlit development experience as smooth as possible, free from unexpected warnings and ready for the future of the library.

Unpacking the plotly_chart Kwargs Deprecation in Streamlit

When we talk about the plotly_chart kwargs deprecation warning in Streamlit, we’re essentially looking at a signal that a specific way of passing additional, non-explicitly defined arguments to st.plotly_chart is no longer recommended and will eventually be removed. For those unfamiliar with Python's **kwargs, it's a powerful feature that allows a function to accept an arbitrary number of keyword arguments, which are then collected into a dictionary. In the context of st.plotly_chart, this mechanism was likely used to forward various Plotly-specific configuration settings that weren't direct parameters of the Streamlit function itself. The Streamlit team, aiming for a cleaner and more explicit API, has introduced a dedicated config argument specifically for passing Plotly configuration options, signaling a move away from using **kwargs for this purpose.

The real head-scratcher, as many developers have pointed out, is when this warning appears even when you're not explicitly passing arbitrary keyword arguments. Instead, you might simply be using a documented parameter like width="content" or height="content". This behavior often feels like a regression, as users diligently follow the official documentation to adapt to previous changes – such as migrating from the deprecated use_container_width=True to the newer width="container" or width="content" – only to be met with another deprecation warning. This creates a frustrating loop where adherence to new guidelines still results in warnings, leading to confusion and unnecessary debugging efforts. The core issue, identified in Streamlit version 1.50.0 and potentially later versions with Python 3.14.2 on macOS 26.1, is that the width parameter, when set to `