Fixing `st.plotly_chart` Kwargs Deprecation In Streamlit

Unraveling the st.plotly_chart Deprecation Warning

Streamlit has revolutionized how data scientists and developers create and share interactive web applications, making complex data visualizations accessible with minimal code. One of its most powerful features is the seamless integration with Plotly, a robust graphing library that allows for incredibly detailed and interactive charts. However, many developers have recently encountered a rather perplexing issue: a kwargs deprecation warning when using st.plotly_chart with documented parameters like width="content". This isn't just a minor annoyance; it’s a source of confusion because users are diligently following the official documentation, yet still receiving warnings about using deprecated keyword arguments.

Imagine you're building a beautiful, responsive dashboard. You want your Plotly charts to adapt perfectly to the container's width, so you naturally reach for width="content" or width="container" in your st.plotly_chart call. You expect smooth sailing, but instead, you're greeted with a message telling you that variable keyword arguments are deprecated and will be removed. This feels contradictory, doesn't it? You're not passing arbitrary keywords; you're using a clearly defined and documented parameter! This article aims to demystify this st.plotly_chart warning, delve into its origin, and provide you with actionable steps to navigate this unexpected behavior. We'll explore why this warning appears, what Streamlit's intentions were with recent API changes, and most importantly, how you can continue building fantastic applications without being bogged down by these deprecation messages. Our goal is to ensure your Streamlit apps remain smooth, efficient, and warning-free, allowing you to focus on delivering high-quality, valuable content to your users.

This particular warning highlights a regression in Streamlit's behavior, meaning something that used to work or should work as intended (according to documentation) is now causing an issue. Understanding this distinction is crucial, as it points to a potential bug rather than an incorrect usage pattern. We'll break down the technical details in a friendly and conversational manner, ensuring that even if you're not a Streamlit or Plotly expert, you'll grasp the core concepts and feel confident in applying the suggested solutions. So, let's dive in and fix those pesky kwargs deprecation warnings once and for all!

Understanding the Root Cause: Why Are We Seeing This Warning?

To truly understand the kwargs deprecation warning in st.plotly_chart, we need to peek behind the curtain of Streamlit's internal workings and how it handles parameters. In Python, **kwargs (keyword arguments) is a powerful mechanism that allows a function to accept an arbitrary number of keyword arguments, which are then passed as a dictionary. This is incredibly flexible but can also lead to ambiguity if not handled carefully. Historically, st.plotly_chart allowed some flexibility with extra kwargs for Plotly configuration, but Streamlit is moving towards a more structured API, recommending the config argument for Plotly-specific options. This is a positive change for maintainability and clarity, but the transition has a hiccup.

The core of the problem lies in a specific piece of code introduced during recent changes in Streamlit's handling of st.plotly_chart. As the provided issue description highlights, an internal check if kwargs: was added. This check is designed to flag any keyword argument passed to st.plotly_chart that isn't explicitly defined as a standard parameter. The intent was to catch old, deprecated kwargs or potential misuses. However, what's happening now is that a newly introduced and fully documented parameter, specifically width="content" (and height), is inadvertently being caught by this general kwargs check. Because width itself is an optional keyword argument, the if kwargs: condition inside Streamlit's st.plotly_chart function interprets it as one of the