Merge pull request #4358 from has2k1/sequence-string

FIX : cbook.is_sequence_of_strings behave better on array/pd.series of strings

doc/users/whats_new/cbook.rst

@@ -0,0 +1,18 @@
+cbook.is_sequence_of_strings recognizes string objects
+``````````````````````````````````````````````````````
+
+This is primarily how pandas stores a sequence of strings.
+
+    import pandas as pd
+    import matplotlib.cbook as cbook
+
+    a = np.array(['a', 'b', 'c'])
+    print(cbook.is_sequence_of_strings(a))  # True
+
+    a = np.array(['a', 'b', 'c'], dtype=object)
+    print(cbook.is_sequence_of_strings(a))  # True
+
+    s = pd.Series(['a', 'b', 'c'])
+    print(cbook.is_sequence_of_strings(s))  # True
+
+Previously, the last two prints returned false.

lib/matplotlib/cbook.py

@@ -783,8 +783,12 @@ def is_sequence_of_strings(obj):
     """
     if not iterable(obj):
         return False
-    if is_string_like(obj):
-        return False
+    if is_string_like(obj) and not isinstance(obj, np.ndarray):
+        try:
+            obj = obj.values
+        except AttributeError:
+            # not pandas
+            return False
     for o in obj:
         if not is_string_like(o):
             return False

lib/matplotlib/tests/test_cbook.py

@@ -26,6 +26,23 @@ def test_is_string_like():
     assert cbook.is_string_like("hello world")
     assert_equal(cbook.is_string_like(10), False)
 
+    y = ['a', 'b', 'c']
+    assert_equal(cbook.is_string_like(y), False)
+
+    y = np.array(y)
+    assert_equal(cbook.is_string_like(y), False)
+
+    y = np.array(y, dtype=object)
+    assert cbook.is_string_like(y)
+
+
+def test_is_sequence_of_strings():
+    y = ['a', 'b', 'c']
+    assert cbook.is_sequence_of_strings(y)
+
+    y = np.array(y, dtype=object)
+    assert cbook.is_sequence_of_strings(y)
+
 
 def test_restrict_dict():
     d = {'foo': 'bar', 1: 2}