Fixed bug #9671 where 'DataFrame.plot()' raised an error when both 'color' and 'style' keywords were passed and there was no color symbol in the style strings (this should be allowed)

Author: David BROCHART

doc/source/whatsnew/v0.16.1.txt

@@ -82,3 +82,5 @@ Bug Fixes
 - Bug in ``Series.quantile`` on empty Series of type ``Datetime`` or ``Timedelta`` (:issue:`9675`)
 - Bug in ``where`` causing incorrect results when upcasting was required (:issue:`9731`)
 - Bug in ``FloatArrayFormatter`` where decision boundary for displaying "small" floats in decimal format is off by one order of magnitude for a given display.precision (:issue:`9764`)
+
+- Fixed bug where ``DataFrame.plot()`` raised an error when both ``color`` and ``style`` keywords were passed and there was no color symbol in the style strings (:issue:`9671`)

pandas/tests/test_graphics.py

@@ -1154,6 +1154,22 @@ def test_plot(self):
         self.assertEqual(len(axes), 1)
         self.assertIs(ax.get_axes(), axes[0])
 
+    def test_color_and_style_arguments(self):
+        df = DataFrame({'x': [1, 2], 'y': [3, 4]})
+        # passing both 'color' and 'style' arguments should be allowed
+        # if there is no color symbol in the style strings:
+        ax = df.plot(color = ['red', 'black'], style = ['-', '--'])
+        # check that the linestyles are correctly set:
+        linestyle = [line.get_linestyle() for line in ax.lines]
+        self.assertEqual(linestyle, ['-', '--'])
+        # check that the colors are correctly set:
+        color = [line.get_color() for line in ax.lines]
+        self.assertEqual(color, ['red', 'black'])
+        # passing both 'color' and 'style' arguments should not be allowed
+        # if there is a color symbol in the style strings:
+        with tm.assertRaises(ValueError):
+            df.plot(color = ['red', 'black'], style = ['k-', 'r--'])
+
     def test_nonnumeric_exclude(self):
         df = DataFrame({'A': ["x", "y", "z"], 'B': [1, 2, 3]})
         ax = df.plot()

pandas/tools/plotting.py

@@ -867,12 +867,17 @@ def _validate_color_args(self):
                           "simultaneously. Using 'color'")
 
         if 'color' in self.kwds and self.style is not None:
+            if com.is_list_like(self.style):
+                styles = self.style
+            else:
+                styles = [self.style]
             # need only a single match
-            if re.match('^[a-z]+?', self.style) is not None:
-                raise ValueError("Cannot pass 'style' string with a color "
-                                 "symbol and 'color' keyword argument. Please"
-                                 " use one or the other or pass 'style' "
-                                 "without a color symbol")
+            for s in styles:
+                if re.match('^[a-z]+?', s) is not None:
+                    raise ValueError("Cannot pass 'style' string with a color "
+                                     "symbol and 'color' keyword argument. Please"
+                                     " use one or the other or pass 'style' "
+                                     "without a color symbol")
 
     def _iter_data(self, data=None, keep_index=False, fillna=None):
         if data is None: