ENH: support str translate for StringMethods

Author: mortada

doc/source/api.rst

@@ -552,6 +552,7 @@ strings and apply several methods to it. These can be acccessed like
    Series.str.strip
    Series.str.swapcase
    Series.str.title
+   Series.str.translate
    Series.str.upper
    Series.str.wrap
    Series.str.zfill

doc/source/text.rst

@@ -268,6 +268,7 @@ Method Summary
     :meth:`~Series.str.rfind`,Equivalent to ``str.rfind``
     :meth:`~Series.str.capitalize`,Equivalent to ``str.capitalize``
     :meth:`~Series.str.swapcase`,Equivalent to ``str.swapcase``
+    :meth:`~Series.str.translate`,Equivalent to ``str.translate``
     :meth:`~Series.str.isalnum`,Equivalent to ``str.isalnum``
     :meth:`~Series.str.isalpha`,Equivalent to ``str.isalpha``
     :meth:`~Series.str.isdigit`,Equivalent to ``str.isdigit``

pandas/core/strings.py

@@ -834,6 +834,65 @@ def str_wrap(arr, width, **kwargs):
     return _na_map(lambda s: '\n'.join(tw.wrap(s)), arr)
 
 
+def str_translate_py3(arr, table):
+    """
+    Map all characters in the string through the given translation table.
+    Equivalent to standard ``str.translate``.
+
+    Parameters
+    ----------
+    table : dict
+        A mapping of Unicode ordinals to Unicode ordinals, strings, or None.
+        nmapped characters are left untouched. Characters mapped to None
+        are deleted.
+
+    Returns
+    -------
+    translated : array
+
+    Notes
+    -----
+    ``str.maketrans`` is a helper function for making translation tables
+    """
+    f = lambda x: x.translate(table)
+    return _na_map(f, arr)
+
+
+def str_translate_py2(arr, table, deletechars=None):
+    """
+    Map all characters in the string through the given translation table and
+    optional argument deletechars. Equivalent to standard ``str.translate``.
+
+    Translate each string such that all characters occurring in the optional
+    argument deletechars are removed, and the remaining characters are mapped
+    through the given translation table, which must be a string of length 256
+    or None. If the table argument is None, no translation is applied and
+    the operation simply removes the characters in deletechars.
+
+    Parameters
+    ----------
+    table : str or None
+        Either a string of length 256 or None.
+        If the table argument is None, no translation is applied and
+        the operation simply removes the characters in deletechars.
+    deletechars : str, optional
+        A string of characters to delete.
+
+    Returns
+    -------
+    translated : array
+
+    Notes
+    -----
+    ``string.maketrans`` is a helper function for making translation tables
+    """
+    if deletechars is None:
+        f = lambda x: x.translate(table)
+    else:
+        f = lambda x: x.translate(table, deletechars)
+    return _na_map(f, arr)
+
+
 def str_get(arr, i):
     """
     Extract element from lists, tuples, or strings in each element in the array
@@ -921,6 +980,24 @@ def wrapper3(self, pat, na=np.nan):
     return wrapper
 
 
+def _str_translate_wrapper():
+    from pandas import compat
+    # python2 has a different signature for str.translate from python3
+    if not compat.PY3:
+        f = str_translate_py2
+        def wrapper(self, table, deletechars=None):
+            result = f(self.series, table, deletechars)
+            return self._wrap_result(result)
+    else:
+        f = str_translate_py3
+        def wrapper(self, table):
+            result = f(self.series, table)
+            return self._wrap_result(result)
+    if f.__doc__:
+        wrapper.__doc__ = f.__doc__
+    return wrapper
+
+
 def copy(source):
     "Copy a docstring from another source function (if present)"
     def do_copy(target):
@@ -1125,6 +1202,7 @@ def get_dummies(self, sep='|'):
     endswith = _pat_wrapper(str_endswith, na=True)
     findall = _pat_wrapper(str_findall, flags=True)
     extract = _pat_wrapper(str_extract, flags=True)
+    translate = _str_translate_wrapper()
 
     _shared_docs['find'] = ("""
     Return %(side)s indexes in each strings where the substring is

pandas/tests/test_strings.py

@@ -965,6 +965,28 @@ def test_pad_fillchar(self):
         with tm.assertRaisesRegexp(TypeError, "fillchar must be a character, not int"):
             result = values.str.pad(5, fillchar=5)
 
+    def test_translate(self):
+        for klass in [Series, Index]:
+            s = klass(['abcdefg', 'abcc', 'cdddfg', 'cdefggg'])
+            if not compat.PY3:
+                import string
+                table = string.maketrans('abc', 'cde')
+            else:
+                table = str.maketrans('abc', 'cde')
+            result = s.str.translate(table)
+            expected = klass(['cdedefg', 'cdee', 'edddfg', 'edefggg'])
+            tm.assert_array_equal(result, expected)
+
+            # python2 only
+            if not compat.PY3:
+                result = s.str.translate(table, 'fg')
+                expected = klass(['cdede', 'cdee', 'eddd', 'ede'])
+                tm.assert_array_equal(result, expected)
+
+                result = s.str.translate(None, 'fg')
+                expected = klass(['abcde', 'abcc', 'cddd', 'cde'])
+                tm.assert_array_equal(result, expected)
+
     def test_center_ljust_rjust(self):
         values = Series(['a', 'b', NA, 'c', NA, 'eeeeee'])