Fix Streamlit Plotly Chart Width Warning
It's a common scenario for developers: you're building a sleek Streamlit app, incorporating interactive plots with Plotly, and suddenly, a cryptic deprecation warning pops up. You're not even explicitly using variable keyword arguments, so what's going on? This article is here to demystify the plotly_chart kwargs deprecation warning in Streamlit, particularly when using the width="content" parameter, and guide you toward a smooth, warning-free experience.
Understanding the plotly_chart Kwargs Deprecation Warning
The core of the issue lies in how Streamlit handles arguments passed to its components, including st.plotly_chart. Plotly charts themselves have a rich set of configuration options, and Streamlit aims to provide a user-friendly way to access these. Historically, st.plotly_chart might have accepted certain arguments directly that were intended for Plotly's internal configuration. As libraries evolve, best practices change, and what was once acceptable might become deprecated to encourage more structured and explicit usage.
The warning message, "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," is a clear indicator of this shift. It suggests that instead of passing configuration details like width or height directly as arguments to st.plotly_chart, these should be encapsulated within a config dictionary. This makes the code cleaner, more organized, and easier to maintain, as all Plotly-specific settings are grouped together.
However, the confusion arises when users encounter this warning even when they are not passing any arbitrary keyword arguments. This is precisely the situation described in the user report: using width="content" (or height="content") triggers the warning. This indicates that the internal implementation of st.plotly_chart might be passing these width or height arguments down to Plotly in a way that the Streamlit warning flags as a deprecated kwargs usage, even if the user intended them as standard parameters.
Why width="content" Triggers the Warning
When you use st.plotly_chart(fig, width="content"), Streamlit interprets width="content" as a directive to automatically adjust the chart's width to fit its container. This is a very useful feature for responsive design in web applications. The warning suggests that, under the hood, Streamlit's mechanism for handling this automatic sizing is being caught by its own deprecation check for kwargs. This isn't necessarily a bug in your code, but rather an artifact of how the feature is implemented within Streamlit and how its warning system is configured.
It's like having a security guard who's a bit too vigilant. They see someone walking through a door they're supposed to guard, and even though the person has a valid pass (width="content" is a documented parameter), the guard flags them because the method of entry looks suspicious based on a new rule.
The Evolution of st.plotly_chart Arguments
Streamlit, like any active open-source project, undergoes frequent updates. These updates often involve refactoring and improving the underlying mechanisms. The deprecation of direct kwargs for st.plotly_chart is part of a broader effort to standardize how external library configurations are passed. Plotly itself has a sophisticated configuration system, and Streamlit's goal is to map these capabilities onto its own components in a clean and future-proof manner.
The introduction of the config argument is the intended solution. Instead of st.plotly_chart(fig, width=500, height=360), the modern approach is st.plotly_chart(fig, config={'width': 500, 'height': 360}). This clearly separates Streamlit's specific display arguments (like use_container_width which is now the preferred way to handle responsive width) from Plotly's internal rendering settings.
When width="content" is used, it's a bit of a hybrid situation. It's a Streamlit-specific parameter for controlling layout, but it also directly influences the visual size of the Plotly chart. The warning appears to be triggered because the way this parameter is passed down to the Plotly engine is being interpreted as a generic keyword argument that is now discouraged.
Reproducing the Warning: A Simple Example
Let's look at the code provided that reliably triggers this warning:
import plotly.graph_objects as go
import streamlit as st
fig = go.Figure()
fig.add_trace(go.Barpolar(r=[1], theta=[0], width=[120]))
fig.update_layout(width=500, height=360) # These are Plotly layout settings
st.plotly_chart(fig, width="content") # This is a Streamlit display parameter
In this example:
fig.update_layout(width=500, height=360)sets the initial dimensions of the Plotly figure itself. These are Plotly-native settings.st.plotly_chart(fig, width="content")instructs Streamlit to render the chart, and specifically requests that its width be set to `
