fix: handle 3-digit shorthand hex in hex_to_rgb

CHANGELOG.md

@@ -4,6 +4,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+### Fixed
+- Fix `hex_to_rgb` parsing of 3-digit shorthand hexadecimal colors such as `#FFF` [[#5662](https://github.com/plotly/plotly.py/pull/5662)], with thanks to @genrichez for the contribution!
+
 
 ## [6.9.0] - 2026-07-09
 

_plotly_utils/colors/__init__.py

@@ -752,11 +752,20 @@ def hex_to_rgb(value):
     """
     Calculates rgb values from a hex color code.
 
-    :param (string) value: Hex color string
+    :param (string) value: Hex color string. May be a full 6-character code
+        or a 3-character shorthand code.
 
     :rtype (tuple) (r_value, g_value, b_value): tuple of rgb values
+
+    Example:
+
+        '#FFFFFF' --> (255, 255, 255)
+        '#FFF'    --> (255, 255, 255)
+
     """
     value = value.lstrip("#")
+    if len(value) == 3:
+        value = "".join(c * 2 for c in value)
     hex_total_length = len(value)
     rgb_section_length = hex_total_length // 3
     return tuple(

plotly/matplotlylib/mpltools.py

@@ -10,6 +10,8 @@
 import warnings
 import matplotlib.dates
 
+from _plotly_utils.colors import hex_to_rgb
+
 
 def check_bar_match(old_bar, new_bar):
     """Check if two bars belong in the same collection (bar chart).
@@ -104,23 +106,6 @@ def convert_symbol(mpl_symbol):
         return "circle"  # default
 
 
-def hex_to_rgb(value):
-    """
-    Change a hex color to an rgb tuple
-
-    :param (str|unicode) value: The hex string we want to convert.
-    :return: (int, int, int) The red, green, blue int-tuple.
-
-    Example:
-
-        '#FFFFFF' --> (255, 255, 255)
-
-    """
-    value = value.lstrip("#")
-    lv = len(value)
-    return tuple(int(value[i : i + lv // 3], 16) for i in range(0, lv, lv // 3))
-
-
 def merge_color_and_opacity(color, opacity):
     """
     Merge hex color with an alpha (opacity) to get an rgba tuple.

tests/test_plotly_utils/colors/test_color_conversions.py

@@ -12,6 +12,15 @@ def test_hex_to_rgb_basic_values():
     assert hex_to_rgb("#aabbcc") == (170, 187, 204)
 
 
+def test_hex_to_rgb_shorthand_3_digit():
+    assert hex_to_rgb("#fff") == (255, 255, 255)
+    assert hex_to_rgb("#000") == (0, 0, 0)
+    assert hex_to_rgb("#abc") == (170, 187, 204)
+    assert hex_to_rgb("#f00") == (255, 0, 0)
+    assert hex_to_rgb("#0f0") == (0, 255, 0)
+    assert hex_to_rgb("#00f") == (0, 0, 255)
+
+
 def test_label_rgb_formats_tuple():
     assert label_rgb((255, 0, 0)) == "rgb(255, 0, 0)"
     assert label_rgb((1, 2, 3)) == "rgb(1, 2, 3)"