str.replace('.','') should replace every character? (fix)

doc/source/whatsnew/v0.24.0.rst

@@ -432,6 +432,30 @@ Backwards incompatible API changes
 
 Pandas 0.24.0 includes a number of API breaking changes.
 
+Replacing strings using Pattern
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Be sure to perform a replace of literal strings by passing the
+regex=False parameter to func:`str.replace`. Mainly when the
+pattern is 1 size string (:issue:`24809`)
+
+Before:
+
+.. ipython:: python
+
+ s = pd.Series(['A|B|C'])
+
+ result = s.str.replace('|', ' ')
+ result
+
+After:
+
+.. ipython:: python
+
+ s = pd.Series(['A|B|C'])
+
+ result = s.str.replace('|', ' ', regex=False)
+ result
 
 .. _whatsnew_0240.api_breaking.deps:
 
@@ -1645,6 +1669,7 @@ Strings
 - Bug in :meth:`Index.str.split` was not nan-safe (:issue:`23677`).
 - Bug :func:`Series.str.contains` not respecting the ``na`` argument for a ``Categorical`` dtype ``Series`` (:issue:`22158`)
 - Bug in :meth:`Index.str.cat` when the result contained only ``NaN`` (:issue:`24044`)
+- Bug in :func:`Series.str.replace` not applying regex in patterns of length 1 (:issue:`24809`)
 
 Interval
 ^^^^^^^^

pandas/core/strings.py

@@ -425,7 +425,7 @@ def str_endswith(arr, pat, na=np.nan):
  return _na_map(f, arr, na, dtype=bool)
 
 
-def str_replace(arr, pat, repl, n=-1, case=None, flags=0, regex=True):
+def str_replace(arr, pat, repl, n=-1, case=None, flags=0, regex=None):
  r"""
  Replace occurrences of pattern/regex in the Series/Index with
  some other string. Equivalent to :meth:`str.replace` or
@@ -564,7 +564,7 @@ def str_replace(arr, pat, repl, n=-1, case=None, flags=0, regex=True):
  # add case flag, if provided
  if case is False:
  flags |= re.IGNORECASE
- if is_compiled_re or len(pat) > 1 or flags or callable(repl):
+ if is_compiled_re or pat or flags or callable(repl):
  n = n if n >= 0 else 0
  compiled = re.compile(pat, flags=flags)
  f = lambda x: compiled.sub(repl=repl, string=x, count=n)
@@ -577,6 +577,9 @@ def str_replace(arr, pat, repl, n=-1, case=None, flags=0, regex=True):
  if callable(repl):
  raise ValueError("Cannot use a callable replacement when "
  "regex=False")
+ if regex==None:
+ warnings.warn("Warning: Interpreting '%s' as a literal, not a regex... " % pat + 
+ "The default will change in the future.", FutureWarning, stacklevel=3)
  f = lambda x: x.replace(pat, repl, n)
 
  return _na_map(f, arr)
@@ -2529,7 +2532,7 @@ def match(self, pat, case=True, flags=0, na=np.nan):
  return self._wrap_result(result, fill_value=na)
 
  @copy(str_replace)
- def replace(self, pat, repl, n=-1, case=None, flags=0, regex=True):
+ def replace(self, pat, repl, n=-1, case=None, flags=0, regex=None):
  result = str_replace(self._parent, pat, repl, n=n, case=case,
  flags=flags, regex=regex)
  return self._wrap_result(result)

pandas/tests/test_strings.py

@@ -1008,6 +1008,21 @@ def test_replace(self):
  values = klass(data)
  pytest.raises(TypeError, values.str.replace, 'a', repl)
 
+ # GH 24804
+ def test_replace_single_pattern(self):
+ values = Series(['abc', '123'])
+
+ result = values.str.replace('.', 'foo', regex=True)
+ expected = Series(['foofoofoo', 'foofoofoo'])
+ tm.assert_series_equal(result, expected)
+
+ def test_replace_without_specifying_regex_parameter(self):
+ values = Series(['a.c'])
+
+ result = values.str.replace('.', 'b')
+ expected = Series(['abc'])
+ tm.assert_series_equal(result, expected) 
+
  def test_replace_callable(self):
  # GH 15055
  values = Series(['fooBAD__barBAD', NA])
@@ -2924,7 +2939,7 @@ def test_pipe_failures(self):
 
  tm.assert_series_equal(result, exp)
 
- result = s.str.replace('|', ' ')
+ result = s.str.replace('|', ' ', regex=False)
  exp = Series(['A B C'])
 
  tm.assert_series_equal(result, exp)