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(WIP) PERF: improve .str perf for all-string values (about 2x-) #10135

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(WIP) PERF: improve .str perf for all-string values (about 2x-) #10135

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41 changes: 30 additions & 11 deletions pandas/core/strings.py
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Original file line number Diff line number Diff line change
Expand Up @@ -116,12 +116,12 @@ def _length_check(others):
return n


def _na_map(f, arr, na_result=np.nan, dtype=object):
def _na_map(f, arr, na_result=np.nan, dtype=object, np_f=None):
# should really _check_ for NA
return _map(f, arr, na_mask=True, na_value=na_result, dtype=dtype)
return _map(f, arr, na_mask=True, na_value=na_result, dtype=dtype, np_f=np_f)


def _map(f, arr, na_mask=False, na_value=np.nan, dtype=object):
def _map(f, arr, na_mask=False, na_value=np.nan, dtype=object, np_f=None):
from pandas.core.series import Series

if not len(arr):
Expand All @@ -131,6 +131,14 @@ def _map(f, arr, na_mask=False, na_value=np.nan, dtype=object):
arr = arr.values
if not isinstance(arr, np.ndarray):
arr = np.asarray(arr, dtype=object)

# short path for all-string array
if np_f is not None and lib.is_string_array(arr):
try:
return np_f(arr.astype(unicode))
except Exception:
pass

if na_mask:
mask = isnull(arr)
try:
Expand Down Expand Up @@ -686,14 +694,17 @@ def str_pad(arr, width, side='left', fillchar=' '):

if side == 'left':
f = lambda x: x.rjust(width, fillchar)
np_f = lambda x: np.core.defchararray.ljust(x, width, fillchar)
elif side == 'right':
f = lambda x: x.ljust(width, fillchar)
np_f = lambda x: np.core.defchararray.rjust(x, width, fillchar)
elif side == 'both':
f = lambda x: x.center(width, fillchar)
np_f = lambda x: np.core.defchararray.lower(x, width, fillchar)
else: # pragma: no cover
raise ValueError('Invalid side')

return _na_map(f, arr)
return _na_map(f, arr, np_f=np_f)


def str_split(arr, pat=None, n=None):
Expand All @@ -720,17 +731,21 @@ def str_split(arr, pat=None, n=None):
if n is None or n == 0:
n = -1
f = lambda x: x.split(pat, n)
np_f = lambda x: np.core.defchararray.split(x, pat, n)
else:
if len(pat) == 1:
if n is None or n == 0:
n = -1
f = lambda x: x.split(pat, n)
np_f = lambda x: np.core.defchararray.split(x, pat, n)
else:
if n is None or n == -1:
n = 0
regex = re.compile(pat)
f = lambda x: regex.split(x, maxsplit=n)
res = _na_map(f, arr)
# numpy doesn't support regex
np_f = None
res = _na_map(f, arr, np_f=np_f)
return res


Expand Down Expand Up @@ -946,7 +961,8 @@ def str_decode(arr, encoding, errors="strict"):
decoded : Series/Index of objects
"""
f = lambda x: x.decode(encoding, errors)
return _na_map(f, arr)
np_f = lambda x: np.core.defchararray.decode(x, errors)
return _na_map(f, arr, np_f=np_f)


def str_encode(arr, encoding, errors="strict"):
Expand All @@ -964,12 +980,13 @@ def str_encode(arr, encoding, errors="strict"):
encoded : Series/Index of objects
"""
f = lambda x: x.encode(encoding, errors)
return _na_map(f, arr)
np_f = lambda x: np.core.defchararray.encode(x, errors)
return _na_map(f, arr, np_f=np_f)


def _noarg_wrapper(f, docstring=None, **kargs):
def _noarg_wrapper(f, docstring=None, np_f=None, **kargs):
def wrapper(self):
result = _na_map(f, self.series, **kargs)
result = _na_map(f, self.series, np_f=np_f, **kargs)
return self._wrap_result(result)

wrapper.__name__ = f.__name__
Expand Down Expand Up @@ -1443,7 +1460,8 @@ def rindex(self, sub, start=0, end=None):
_shared_docs['swapcase'] = dict(type='be swapcased', method='swapcase')
lower = _noarg_wrapper(lambda x: x.lower(),
docstring=_shared_docs['casemethods'] %
_shared_docs['lower'])
_shared_docs['lower'],
np_f=np.core.defchararray.lower)
upper = _noarg_wrapper(lambda x: x.upper(),
docstring=_shared_docs['casemethods'] %
_shared_docs['upper'])
Expand All @@ -1452,7 +1470,8 @@ def rindex(self, sub, start=0, end=None):
_shared_docs['title'])
capitalize = _noarg_wrapper(lambda x: x.capitalize(),
docstring=_shared_docs['casemethods'] %
_shared_docs['capitalize'])
_shared_docs['capitalize'],
np_f=np.core.defchararray.capitalize)
swapcase = _noarg_wrapper(lambda x: x.swapcase(),
docstring=_shared_docs['casemethods'] %
_shared_docs['swapcase'])
Expand Down