Streamlit Plotly_chart Kwargs Deprecation Warning

When you're building interactive dashboards with Streamlit, you want things to be smooth and seamless. You've probably spent a good amount of time tweaking your visualizations to look just right, and using st.plotly_chart is a fantastic way to integrate Plotly charts into your apps. However, some users have encountered a rather persistent deprecation warning related to kwargs (keyword arguments) even when they're not explicitly passing any. This can be confusing, especially when you're just trying to set the width or height of your chart using documented parameters like width="content". Let's dive into what's causing this warning and how you can resolve it to keep your Streamlit apps clean and warning-free.

Understanding the "Kwargs Deprecation Warning" in Streamlit

The kwargs deprecation warning specifically arises from changes made within Streamlit's st.plotly_chart function. Streamlit is constantly evolving, and with new versions come updates and improvements. Sometimes, these updates involve refactoring how functions handle arguments. In this case, the warning indicates that the way variable keyword arguments are being handled is slated for removal in a future release. The message usually suggests using the config argument instead for Plotly-specific configurations. However, the crux of the issue for many users is that this warning pops up even when they aren't using variable keyword arguments at all. They are using parameters like width or height that are directly documented and supported by st.plotly_chart.

This situation is a bit of a head-scratcher because the warning seems to be triggered incorrectly. The code snippet provided in the discussion shows a conditional check: if kwargs:. This implies that the warning should only be displayed if there are actual extra, undefined keyword arguments passed to the function. Yet, users are reporting the warning appearing even when they pass a seemingly valid argument like width="content" or height=360. This suggests that either the check for kwargs is being triggered erroneously, or there's a misunderstanding about which arguments are being treated as kwargs internally by Streamlit. The warning itself is a heads-up that relying on passing arbitrary keyword arguments directly to st.plotly_chart for Plotly's internal configuration might not be the best long-term strategy. Instead, Streamlit wants users to leverage the dedicated config parameter for these Plotly settings.

Why is this a problem? A clean console output is crucial for debugging and for presenting a professional application. Unnecessary warnings can obscure real issues or simply be an annoyance. Moreover, if a documented feature like setting the width is triggering a deprecation warning, it can lead users to believe the feature itself is deprecated or buggy, which is not the intended outcome. It's about ensuring that documented functionalities work as expected without generating misleading messages. The goal is to have Streamlit clearly communicate when a user is doing something that will be removed, not when they are using current, supported features.

The Root Cause: How width="content" Triggers the Warning

The specific trigger for this kwargs deprecation warning when using width="content" (or height="content") lies in how Streamlit internally processes these arguments. While width and height are documented parameters for st.plotly_chart when you're setting explicit pixel values (e.g., width=500), using the string "content" might be interpreted differently by Streamlit's argument parsing mechanism. It's possible that when "content" is passed, Streamlit's internal logic bundles it, or other parameters it might be processing alongside it, into the kwargs dictionary, thereby triggering the if kwargs: condition. This means that even though you, as the user, are providing a valid and documented value for width, Streamlit's internal handling mistakenly flags it as an undefined or variable keyword argument.

This behavior is particularly problematic because it deviates from the expected functionality. Users consult the documentation, see that width="content" is a supported way to make a Plotly chart dynamically adjust its width to its container, and proceed to use it. The expectation is that documented parameters, even those that are strings, should not trigger deprecation warnings related to variable keyword arguments. The warning's purpose is to guide developers away from passing arguments that Plotly itself might not recognize or that Streamlit intends to manage differently in the future, such as **plot_options that are not explicitly handled. However, when a parameter like width="content" is a first-class citizen in the Streamlit API for st.plotly_chart, it shouldn't fall into the category of