ENH: Add StringMethods.capitalize and swapcase

Author: sinhrks

doc/source/api.rst

@@ -521,6 +521,7 @@ strings and apply several methods to it. These can be acccessed like
    :toctree: generated/
    :template: autosummary/accessor_method.rst
 
+   Series.str.capitalize
    Series.str.cat
    Series.str.center
    Series.str.contains
@@ -549,6 +550,7 @@ strings and apply several methods to it. These can be acccessed like
    Series.str.split
    Series.str.startswith
    Series.str.strip
+   Series.str.swapcase
    Series.str.title
    Series.str.upper
    Series.str.zfill

doc/source/text.rst

@@ -233,6 +233,8 @@ Method Summary
     :meth:`~Series.str.upper`,Equivalent to ``str.upper``
     :meth:`~Series.str.find`,Equivalent to ``str.find``
     :meth:`~Series.str.rfind`,Equivalent to ``str.rfind``
+    :meth:`~Series.str.capicalize`,Equivalent to ``str.capitalize``
+    :meth:`~Series.str.swapcase`,Equivalent to ``str.swapcase``
     :meth:`~Series.str.isalnum`,Equivalent to ``str.isalnum``
     :meth:`~Series.str.isalpha`,Equivalent to ``str.isalpha``
     :meth:`~Series.str.isdigit`,Equivalent to ``str.isdigit``

doc/source/whatsnew/v0.16.1.txt

@@ -17,6 +17,8 @@ We recommend that all users upgrade to this version.
 Enhancements
 ~~~~~~~~~~~~
 
+- Added ``StringMethods.capitalize()`` and ``swapcase`` which behave as the same as standard ``str`` (:issue:`9766`)
+
 
 
 
@@ -58,7 +60,7 @@ Performance Improvements
 Bug Fixes
 ~~~~~~~~~
 
-- Fixed bug (:issue:`9542`) where labels did not appear properly in legend of ``DataFrame.plot()``. Passing ``label=`` args also now works, and series indices are no longer mutated. 
+- Fixed bug (:issue:`9542`) where labels did not appear properly in legend of ``DataFrame.plot()``. Passing ``label=`` args also now works, and series indices are no longer mutated.
 
 
 

pandas/core/strings.py

@@ -1157,18 +1157,28 @@ def rfind(self, sub, start=0, end=None):
     len = _noarg_wrapper(len, docstring=_shared_docs['len'], dtype=int)
 
     _shared_docs['casemethods'] = ("""
-    Convert strings in array to %s
+    Convert strings in array to %(type)s.
+    Equivalent to ``str.%(method)s``.
 
     Returns
     -------
-    uppercase : array
+    converted : array
     """)
+    _shared_docs['lower'] = dict(type='lowercase', method='lower')
+    _shared_docs['upper'] = dict(type='uppercase', method='upper')
+    _shared_docs['title'] = dict(type='titlecase', method='title')
+    _shared_docs['capitalize'] = dict(type='be capitalized', method='capitalize')
+    _shared_docs['swapcase'] = dict(type='be swapcased', method='swapcase')
     lower = _noarg_wrapper(lambda x: x.lower(),
-                           docstring=_shared_docs['casemethods'] % 'lowercase')
+                           docstring=_shared_docs['casemethods'] % _shared_docs['lower'])
     upper = _noarg_wrapper(lambda x: x.upper(),
-                           docstring=_shared_docs['casemethods'] % 'uppercase')
+                           docstring=_shared_docs['casemethods'] % _shared_docs['upper'])
     title = _noarg_wrapper(lambda x: x.title(),
-                           docstring=_shared_docs['casemethods'] % 'titlecase')
+                           docstring=_shared_docs['casemethods'] % _shared_docs['title'])
+    capitalize = _noarg_wrapper(lambda x: x.capitalize(),
+                                docstring=_shared_docs['casemethods'] % _shared_docs['capitalize'])
+    swapcase = _noarg_wrapper(lambda x: x.swapcase(),
+                              docstring=_shared_docs['casemethods'] % _shared_docs['swapcase'])
 
     _shared_docs['ismethods'] = ("""
     Check whether all characters in each string in the array are %(type)s.

pandas/tests/test_strings.py

@@ -328,6 +328,53 @@ def test_lower_upper(self):
         result = result.str.lower()
         tm.assert_series_equal(result, values)
 
+    def test_capitalize(self):
+        values = Series(["FOO", "BAR", NA, "Blah", "blurg"])
+        result = values.str.capitalize()
+        exp = Series(["Foo", "Bar", NA, "Blah", "Blurg"])
+        tm.assert_series_equal(result, exp)
+
+        # mixed
+        mixed = Series(["FOO", NA, "bar", True, datetime.today(),
+                        "blah", None, 1, 2.])
+        mixed = mixed.str.capitalize()
+        exp = Series(["Foo", NA, "Bar", NA, NA, "Blah", NA, NA, NA])
+        tm.assert_almost_equal(mixed, exp)
+
+        # unicode
+        values = Series([u("FOO"), NA, u("bar"), u("Blurg")])
+        results = values.str.capitalize()
+        exp = Series([u("Foo"), NA, u("Bar"), u("Blurg")])
+        tm.assert_series_equal(results, exp)
+
+    def test_swapcase(self):
+        values = Series(["FOO", "BAR", NA, "Blah", "blurg"])
+        result = values.str.swapcase()
+        exp = Series(["foo", "bar", NA, "bLAH", "BLURG"])
+        tm.assert_series_equal(result, exp)
+
+        # mixed
+        mixed = Series(["FOO", NA, "bar", True, datetime.today(),
+                        "Blah", None, 1, 2.])
+        mixed = mixed.str.swapcase()
+        exp = Series(["foo", NA, "BAR", NA, NA, "bLAH", NA, NA, NA])
+        tm.assert_almost_equal(mixed, exp)
+
+        # unicode
+        values = Series([u("FOO"), NA, u("bar"), u("Blurg")])
+        results = values.str.swapcase()
+        exp = Series([u("foo"), NA, u("BAR"), u("bLURG")])
+        tm.assert_series_equal(results, exp)
+
+    def test_casemethods(self):
+        values = ['aaa', 'bbb', 'CCC', 'Dddd', 'eEEE']
+        s = Series(values)
+        self.assertEqual(s.str.lower().tolist(), [v.lower() for v in values])
+        self.assertEqual(s.str.upper().tolist(), [v.upper() for v in values])
+        self.assertEqual(s.str.title().tolist(), [v.title() for v in values])
+        self.assertEqual(s.str.capitalize().tolist(), [v.capitalize() for v in values])
+        self.assertEqual(s.str.swapcase().tolist(), [v.swapcase() for v in values])
+
     def test_replace(self):
         values = Series(['fooBAD__barBAD', NA])
 
@@ -636,6 +683,8 @@ def test_empty_str_methods(self):
         tm.assert_series_equal(empty_str, empty.str.istitle())
         tm.assert_series_equal(empty_str, empty.str.isnumeric())
         tm.assert_series_equal(empty_str, empty.str.isdecimal())
+        tm.assert_series_equal(empty_str, empty.str.capitalize())
+        tm.assert_series_equal(empty_str, empty.str.swapcase())
 
     def test_ismethods(self):
         values = ['A', 'b', 'Xy', '4', '3A', '', 'TT', '55', '-', '  ']