From 7f3f25c8450f414f3baa3e23a17be7da84b89572 Mon Sep 17 00:00:00 2001
From: Rami Developer <rami.dev@example.com>
Date: Thu, 5 Feb 2026 14:35:00 -0600
Subject: [PATCH] fix: don't modify global warnings.formatwarning (fixes #5472)

Remove global modification of warnings.formatwarning from:
- plotly/tools.py
- plotly/matplotlylib/renderer.py

The previous implementation was setting warnings.formatwarning to a custom
function at module import time, which changed the warning format for all
warnings in the Python process, not just plotly's warnings.

This fix ensures plotly doesn't interfere with Python's default warning
format or any custom format set by the user.

Added test to verify warnings.formatwarning is not modified by plotly imports.
---
 CHANGELOG.md                            |  3 ++
 plotly/matplotlylib/renderer.py         |  8 ---
 plotly/tools.py                         |  8 ---
 tests/test_core/test_warnings_format.py | 65 +++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 16 deletions(-)
 create mode 100644 tests/test_core/test_warnings_format.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2b0d878b358..aefb4c603b8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+### Fixed
+- Fix issue where plotly was changing the global warnings format [[#5472](https://github.com/plotly/plotly.py/issues/5472)]
+
 ## [6.5.2] - 2026-01-14
 
 ### Fixed
diff --git a/plotly/matplotlylib/renderer.py b/plotly/matplotlylib/renderer.py
index d55f86ef3c2..71f5b207db0 100644
--- a/plotly/matplotlylib/renderer.py
+++ b/plotly/matplotlylib/renderer.py
@@ -14,14 +14,6 @@
 from plotly.matplotlylib import mpltools
 
 
-# Warning format
-def warning_on_one_line(msg, category, filename, lineno, file=None, line=None):
-    return "%s:%s: %s:\n\n%s\n\n" % (filename, lineno, category.__name__, msg)
-
-
-warnings.formatwarning = warning_on_one_line
-
-
 class PlotlyRenderer(Renderer):
     """A renderer class inheriting from base for rendering mpl plots in plotly.
 
diff --git a/plotly/tools.py b/plotly/tools.py
index 67f828204d7..b0875507439 100644
--- a/plotly/tools.py
+++ b/plotly/tools.py
@@ -55,14 +55,6 @@
 ALTERNATIVE_HISTNORM = "probability"
 
 
-# Warning format
-def warning_on_one_line(message, category, filename, lineno, file=None, line=None):
-    return "%s:%s: %s:\n\n%s\n\n" % (filename, lineno, category.__name__, message)
-
-
-warnings.formatwarning = warning_on_one_line
-
-
 ### mpl-related tools ###
 def mpl_to_plotly(fig, resize=False, strip_style=False, verbose=False):
     """Convert a matplotlib figure to plotly dictionary and send.
diff --git a/tests/test_core/test_warnings_format.py b/tests/test_core/test_warnings_format.py
new file mode 100644
index 00000000000..b68c5f7595e
--- /dev/null
+++ b/tests/test_core/test_warnings_format.py
@@ -0,0 +1,65 @@
+"""Test that plotly doesn't modify global warnings format (Issue #5472)"""
+import warnings
+import sys
+from unittest import TestCase
+
+
+class TestWarningsFormat(TestCase):
+    """Test that importing plotly modules doesn't change warnings.formatwarning"""
+
+    def test_import_plotly_does_not_change_warnings_format(self):
+        """Importing plotly should not modify the global warnings format"""
+        # Store the original format
+        original_format = warnings.formatwarning
+        
+        # Import plotly modules that previously modified warnings.formatwarning
+        # We need to reimport to test the current code state
+        import importlib
+        
+        # Force reimport of tools module to test current state
+        if 'plotly.tools' in sys.modules:
+            importlib.reload(sys.modules['plotly.tools'])
+        else:
+            import plotly.tools
+            
+        # Check that warnings.formatwarning is still the original
+        self.assertIs(
+            warnings.formatwarning, 
+            original_format,
+            "Importing plotly.tools changed warnings.formatwarning globally"
+        )
+        
+    def test_import_matplotlylib_renderer_does_not_change_warnings_format(self):
+        """Importing matplotlylib.renderer should not modify the global warnings format"""
+        # Store the original format
+        original_format = warnings.formatwarning
+        
+        import importlib
+        
+        # Force reimport of renderer module to test current state  
+        if 'plotly.matplotlylib.renderer' in sys.modules:
+            importlib.reload(sys.modules['plotly.matplotlylib.renderer'])
+        else:
+            import plotly.matplotlylib.renderer
+            
+        # Check that warnings.formatwarning is still the original
+        self.assertIs(
+            warnings.formatwarning,
+            original_format,
+            "Importing plotly.matplotlylib.renderer changed warnings.formatwarning globally"
+        )
+
+    def test_warnings_format_unchanged_after_multiple_imports(self):
+        """Multiple imports should not change warnings format"""
+        original_format = warnings.formatwarning
+        
+        # Import both modules
+        import plotly.tools
+        import plotly.matplotlylib.renderer
+        
+        # Verify format is unchanged
+        self.assertIs(
+            warnings.formatwarning,
+            original_format,
+            "warnings.formatwarning was changed after importing plotly modules"
+        )