Resolve `st.plotly_chart` `kwargs` Warning With `width='content'`

Unpacking the st.plotly_chart kwargs Deprecation Warning

If you've been working with Streamlit and Plotly, you might have recently encountered a rather perplexing kwargs deprecation warning when using st.plotly_chart, especially when trying to adjust its display size with parameters like width="content". It's a common scenario: you meticulously follow the documentation, using width="content" to ensure your beautiful Plotly chart dynamically adjusts to its container, only to be met with a warning message about variable keyword arguments being deprecated. This can be incredibly confusing and frustrating, as you're not explicitly passing any **kwargs in your code. The warning typically states something along the lines of, "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." The core of the confusion here is that width is a documented and valid parameter for st.plotly_chart within Streamlit, not a generic catch-all for Plotly's internal configurations. Developers are often left wondering if they're doing something wrong or if the library itself has a bug. This unexpected alert can lead to unnecessary debugging efforts, where you scrutinize your code for hidden kwargs that simply don't exist. It interrupts the smooth development flow, making what should be a straightforward task — rendering an interactive chart with a responsive width — feel like navigating a minefield. Understanding why this warning appears, despite your correct usage of width="content", is the first step towards effectively addressing it and maintaining a clean, warning-free Streamlit application. This situation highlights a transitional phase in Streamlit's API, where the underlying mechanisms might interpret certain legitimate parameters in a way that triggers a broad deprecation notice, even when the intent of the warning isn't directly applicable to your specific parameter.

Understanding the Root Cause: Streamlit's Internal kwargs Handling

To truly grasp why the st.plotly_chart kwargs deprecation warning surfaces even with width="content", we need to delve a little deeper into Streamlit's internal mechanics. Historically, Streamlit provided a use_container_width=True parameter for st.plotly_chart to make charts expand to their container's full width. As Streamlit evolves, this boolean flag has been superseded by the more flexible width (and height) parameters, allowing for finer control over component sizing, including the very popular width="content" option. The root cause of the deprecation warning, however, lies in how Streamlit's st.plotly_chart function processes its arguments internally. The Streamlit team introduced a warning mechanism to gently guide developers away from passing Plotly-specific configuration options directly as keyword arguments to st.plotly_chart. Instead, these Plotly configurations should ideally be encapsulated within the config dictionary argument. The problem arises because the internal logic responsible for detecting generic kwargs is sometimes overly broad. When an argument like width="content" is passed – which, remember, is a perfectly valid and documented Streamlit display parameter – it might, under certain internal conditions or specific versions of Streamlit, get inadvertently caught by the if kwargs: check within Streamlit's source code. This if kwargs: condition, as you observed in the reproducible code example, is designed to trigger the deprecation warning whenever any unexpected keyword argument is detected that isn't explicitly defined as a Streamlit parameter. So, even though width is a legitimate parameter for st.plotly_chart in the Streamlit API, the warning appears because the internal parsing for kwargs might misclassify it as a generic, Plotly-bound argument during the deprecation transition. This creates a confusing experience where a user adheres to the documentation but still receives a warning intended for a different use case. It's a classic example of a necessary, but sometimes overzealous, warning system during a library's API evolution.

Effective Strategies to Resolve the st.plotly_chart Warning

Effectively resolving the persistent st.plotly_chart kwargs deprecation warning, particularly when using width="content", involves a few strategic approaches. The first and often simplest solution is to ensure you are running the absolute latest stable version of Streamlit. Deprecation warnings, especially those that misfire for documented parameters, are frequently patched and refined in subsequent releases as the library matures. So, a quick pip install --upgrade streamlit might be all you need to silence the unwarranted warning. If the warning persists, it's crucial to understand the intended separation of concerns: Streamlit handles how a component fits into your app layout, while Plotly handles the internal rendering and configuration of the chart itself. For instance, if you're trying to set global Plotly options like enabling scroll zoom or a specific button configuration, these should be passed via the config dictionary argument of st.plotly_chart. For example, instead of st.plotly_chart(fig, showLink=False), you would use st.plotly_chart(fig, config={'displaylogo': False, 'displayModeBar': True}). However, width="content" is specifically a Streamlit parameter controlling the component's width within the Streamlit layout, not a Plotly figure configuration. Therefore, it should not be moved into the config dictionary. If width="content" continues to trigger the warning, consider whether it's truly essential for your layout. Sometimes, simply relying on the default rendering of st.plotly_chart after setting your Plotly figure's layout via fig.update_layout(width=None, height=None, autosize=True) can achieve a similar responsive effect without Streamlit's explicit width parameter, thus avoiding the warning. Alternatively, providing a fixed width (e.g., width=800) to st.plotly_chart might bypass the