Streamlit: Fix Plotly Chart Kwargs Deprecation Warning

Understanding the plotly_chart Kwargs Deprecation Warning in Streamlit

Hey there, Streamlit enthusiasts! Have you ever been happily crafting your interactive dashboards, only to be met with a slightly alarming deprecation warning when using st.plotly_chart? Specifically, when you try to adjust the width or height of your charts using parameters like width="content", a warning pops up. This warning talks about kwargs being deprecated, which can be a bit confusing, especially when you're confident you're only using the documented parameters and haven't explicitly passed any variable keyword arguments. It's like getting a "Beware of the dog" sign on a perfectly friendly poodle – a bit unexpected and potentially misleading. This article dives deep into this specific Streamlit behavior, clarifies why it's happening, and how you can navigate it smoothly. We'll ensure you understand the underlying reasons and provide clear, actionable steps to keep your Streamlit apps running without these unnecessary warnings, ensuring a cleaner and more professional presentation of your data visualizations. We want to make sure your journey with Streamlit is as seamless as possible, and that includes understanding and resolving any little bumps in the road, like this kwargs warning. So, let's get to the bottom of this, shall we?

Why the kwargs Warning Appears

Let's unpack why you might be seeing this kwargs deprecation warning even when you're not using them directly. The core of the issue lies in how Streamlit's st.plotly_chart function handles its arguments, especially concerning the dimensions of the plots. When you pass width="content" or height="auto" (or any other predefined string values for these parameters), Streamlit interprets these as arguments that are being passed down to the underlying Plotly chart configuration. In older versions or perhaps in a previous implementation detail, these dimension-related arguments might have been treated as general keyword arguments (kwargs). As Streamlit evolves, it refines its API to be more explicit and organized. The kwargs were being used to pass certain configurations, including layout options like width and height, directly to the plotly_chart function. However, the developers decided to streamline this by introducing a dedicated config argument for Plotly-specific configurations. The warning you're encountering is a byproduct of this transition. Even though you're using a documented and intended way to set the chart's dimensions, the internal mechanism might still be checking for or processing these arguments in a way that triggers the kwargs deprecation logic. It's a bit of a catch-22: you're doing the right thing according to the documentation, but the system's internal checks are flagging it based on its evolving architecture. This isn't necessarily a bug in your code, but rather a signal that the way arguments are being handled internally is changing. The warning message is designed to guide users towards the new, preferred method of passing configurations, which is through the config dictionary. So, while it might seem like an error in your usage, it's more of an artifact of Streamlit's ongoing development and API cleanup. The team aims to make the API more predictable and easier to manage, and this warning is part of that process. It's a gentle nudge to adapt to the new patterns as they emerge, ensuring your code remains compatible and efficient in future versions of Streamlit. Understanding this distinction between how arguments are processed internally and how you're intended to use them is key to demystifying this warning and continuing your development with confidence. We'll explore how to effectively use the config argument to avoid this warning in the next section, turning this potential confusion into a learning opportunity about Streamlit's best practices.

Implementing the config Argument: The Correct Approach

The recommended way to handle Plotly chart configurations, including dimensions, and to avoid the kwargs deprecation warning is by utilizing the config argument within st.plotly_chart. This config argument accepts a Python dictionary where you can specify various Plotly-related settings. For controlling the width and height of your chart, you'll pass these values within this dictionary. Instead of directly providing width="content" as an argument to st.plotly_chart, you'll now pass it as config={'width': 'content'} or config={'height': 'auto'}. Let's look at the reproducible code example provided in the issue and adapt it to use the config argument correctly. Previously, you might have written st.plotly_chart(fig, width="content"). The updated and correct way to achieve the same result without triggering the deprecation warning is st.plotly_chart(fig, config={'width': 'content'}). Similarly, if you wanted to control the height, you would use st.plotly_chart(fig, config={'height': 'auto'}). It's important to note that the width and height parameters you might be familiar with from Plotly's own update_layout function are distinct from the arguments passed to st.plotly_chart for controlling the display size within the Streamlit app. While fig.update_layout(width=500, height=360) sets the intrinsic dimensions of the Plotly figure, the config argument in st.plotly_chart dictates how that figure is rendered within the Streamlit environment. This means you can set a figure's internal layout dimensions and then control its display size in Streamlit independently. For example, you could have a figure with a default layout size, but then use st.plotly_chart(fig, config={'width': 800, 'height': 400}) to make it appear larger or smaller on your Streamlit page. This provides a flexible way to manage the visual presentation of your charts. By consistently using the config dictionary for all Plotly-specific settings that are passed to st.plotly_chart, you align your code with Streamlit's current best practices and ensure compatibility with future updates. This approach not only resolves the deprecation warning but also makes your code more readable and maintainable, clearly separating Streamlit-specific display controls from Plotly figure configurations. It's a small change that brings significant clarity and robustness to your data visualization code. Embracing this method will help you maintain a clean codebase and avoid unexpected warnings as you continue to build sophisticated Streamlit applications.

Understanding Deprecations and API Evolution in Streamlit

Deprecation warnings in software development are like gentle nudges from the developers, signaling that a particular feature or method is on its way out. They aren't errors that will immediately break your code, but they indicate that the way you're currently doing something might become unsupported in future versions. Streamlit, like any actively developed framework, undergoes continuous evolution. Its developers are constantly working to improve the library, introduce new features, enhance performance, and, importantly, refine the API for better usability and maintainability. The kwargs deprecation warning related to st.plotly_chart is a prime example of this API evolution. In the past, Streamlit might have relied more heavily on general keyword arguments (kwargs) to pass various settings to its components. This can be flexible but can also lead to ambiguity and make it harder to track which arguments are truly supported and how they are processed. To address this, Streamlit is moving towards more explicit argument handling. For st.plotly_chart, this means directing Plotly-specific configurations, such as width, height, responsive, and others, into a dedicated config dictionary. This makes the function signature cleaner and clearly delineates between Streamlit's own arguments (like use_container_width, which is now deprecated in favor of direct width/height in config) and Plotly's internal settings. When you see a deprecation warning, it's a good practice to pay attention to it. The warning message often provides clues about the alternative or preferred method. In this case, the warning explicitly suggests using the config argument. Ignoring these warnings might lead to your application breaking when you eventually update Streamlit to a version where the deprecated feature is completely removed. By proactively addressing deprecation warnings, you ensure that your Streamlit applications remain robust, up-to-date, and compatible with the latest features and improvements. It's an investment in the long-term health and maintainability of your project. Think of it as a maintenance task for your code, ensuring it stays in good working order. This iterative process of refinement is what keeps Streamlit a powerful and user-friendly tool for building data apps. Understanding the