Fixing Streamlit's Plotly Chart `kwargs` Deprecation Warning
Ever been working on your awesome Streamlit app, trying to get that perfect Plotly chart to display just right, only to be hit with a pesky kwargs deprecation warning? Specifically, when you're using st.plotly_chart and setting parameters like width="content" or height? You're not alone! This warning can be a bit confusing, especially when you feel like you're following the documentation. Let's dive deep into what this warning means, why it's happening, and most importantly, how to fix it to keep your Streamlit applications running smoothly and warning-free.
Understanding the Streamlit plotly_chart Deprecation Warning
When you encounter the Streamlit plotly_chart deprecation warning related to kwargs, it can feel a little bewildering, especially when you're diligently using documented parameters like width="content". At its core, st.plotly_chart is Streamlit's fantastic way of seamlessly embedding interactive Plotly visualizations directly into your web applications. Plotly itself is a powerful graphing library, and st.plotly_chart acts as a bridge, making it super easy to bring those beautiful charts to life within your Streamlit dashboards. A deprecation warning, in the world of software development, is essentially a heads-up from the library developers. It tells you that a particular feature, function, or way of doing things is still working for now, but it's considered outdated and will be removed or changed in a future release. It's their way of guiding you towards a newer, often better, and more maintainable approach. Ignoring these warnings isn't a good idea, as your code might suddenly break during a future upgrade. The specific warning we're discussing here revolves around **kwargs, which in Python, is a special syntax that allows a function to accept an arbitrary number of keyword arguments. Think of it as a flexible catcher for any extra keyword-value pairs you pass to a function that aren't explicitly defined in its signature. While incredibly flexible, using **kwargs extensively can sometimes make API design less strict, as it allows users to pass undefined parameters without immediate errors, potentially leading to hard-to-debug issues down the line or making future API changes more difficult for the library developers.
The peculiar part of this deprecation warning is that it triggers even when you’re using width="content", which is a perfectly documented parameter for st.plotly_chart. This suggests that width (and height) might have been internally treated as part of the **kwargs collection, even though they have dedicated parameter slots. The provided reproducible code example perfectly illustrates this: st.plotly_chart(fig, width="content") clearly shows a documented parameter being used, yet it still throws the warning. The warning message itself clearly 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." This message indicates a shift in how Streamlit wants you to pass certain parameters, especially those that might configure the underlying Plotly chart's display, rather than Streamlit's container. The current behavior is that even with seemingly valid, documented arguments, the warning appears, while the expected behavior is that using documented parameters should never trigger a deprecation warning. This discrepancy highlights a potential internal implementation detail where Streamlit is trying to streamline its API. For developers, the implication is clear: even if your app works now, this warning is a ticking clock, and understanding the new config argument for Plotly-specific settings is paramount to future-proofing your data visualization components in Streamlit.
Deep Dive into Python's **kwargs and Streamlit's Approach
Let's unpack what **kwargs really means in Python, and how Streamlit's evolving approach to its plotly_chart function reflects broader best practices in library development. In Python, **kwargs (short for
