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Jul 20, 2015
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PERF: Improve perf of to_datetime with ISO format #10615

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.17.0.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -328,6 +328,7 @@ Performance Improvements
- Significantly improved performance of indexing ``MultiIndex`` with slicers (:issue:`10287`)
- Improved performance of ``Series.isin`` for datetimelike/integer Series (:issue:`10287`)
- 20x improvement in ``concat`` of Categoricals when categories are identical (:issue:`10587`)
- Improved performance of ``to_datetime`` when specified format string is ISO8601 (:issue:`10178`)


.. _whatsnew_0170.bug_fixes:
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24 changes: 19 additions & 5 deletions pandas/tseries/tests/test_timeseries.py
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Expand Up @@ -919,8 +919,8 @@ def test_to_datetime_with_apply(self):
assert_series_equal(result, expected)

td = pd.Series(['May 04', 'Jun 02', ''], index=[1,2,3])
self.assertRaises(ValueError, lambda : pd.to_datetime(td,format='%b %y'))
self.assertRaises(ValueError, lambda : td.apply(pd.to_datetime, format='%b %y'))
self.assertRaises(ValueError, lambda : pd.to_datetime(td,format='%b %y', errors='raise'))
self.assertRaises(ValueError, lambda : td.apply(pd.to_datetime, format='%b %y', errors='raise'))
expected = pd.to_datetime(td, format='%b %y', coerce=True)

result = td.apply(lambda x: pd.to_datetime(x, format='%b %y', coerce=True))
Expand Down Expand Up @@ -4197,6 +4197,20 @@ def test_to_datetime_format_YYYYMMDD(self):
expected = Series(['20121231','20141231','NaT'],dtype='M8[ns]')
assert_series_equal(result, expected)

# GH 10178
def test_to_datetime_format_integer(self):
s = Series([2000, 2001, 2002])
expected = Series([ Timestamp(x) for x in s.apply(str) ])

result = to_datetime(s,format='%Y')
assert_series_equal(result, expected)

s = Series([200001, 200105, 200206])
expected = Series([ Timestamp(x[:4] + '-' + x[4:]) for x in s.apply(str) ])

result = to_datetime(s,format='%Y%m')
assert_series_equal(result, expected)

def test_to_datetime_format_microsecond(self):
val = '01-Apr-2011 00:00:01.978'
format = '%d-%b-%Y %H:%M:%S.%f'
Expand Down Expand Up @@ -4524,9 +4538,9 @@ def test_day_not_in_month_coerce_false_raise(self):

def test_day_not_in_month_coerce_false_ignore(self):
self.assertEqual(to_datetime('2015-02-29', errors='ignore', coerce=False), '2015-02-29')
self.assertRaises(ValueError, to_datetime, '2015-02-29', errors='ignore', format="%Y-%m-%d", coerce=False)
self.assertRaises(ValueError, to_datetime, '2015-02-32', errors='ignore', format="%Y-%m-%d", coerce=False)
self.assertRaises(ValueError, to_datetime, '2015-04-31', errors='ignore', format="%Y-%m-%d", coerce=False)
self.assertEqual(to_datetime('2015-02-29', errors='ignore', format="%Y-%m-%d", coerce=False), '2015-02-29')
self.assertEqual(to_datetime('2015-02-32', errors='ignore', format="%Y-%m-%d", coerce=False), '2015-02-32')
self.assertEqual(to_datetime('2015-04-31', errors='ignore', format="%Y-%m-%d", coerce=False), '2015-04-31')

if __name__ == '__main__':
nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],
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39 changes: 23 additions & 16 deletions pandas/tseries/tools.py
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Expand Up @@ -296,21 +296,24 @@ def _convert_listlike(arg, box, format):
return result

arg = com._ensure_object(arg)
require_iso8601 = False

if infer_datetime_format and format is None:
format = _guess_datetime_format_for_array(arg, dayfirst=dayfirst)
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maybe this should be:

if format is None:

    if infer_datetime_format:
           .......
    else:
          # check for the iso format

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I think the iso format code needs to be outside the else - it should apply whether or not the format was inferred or specified?


if format is not None:
# There is a special fast-path for iso8601 formatted
# datetime strings, so in those cases don't use the inferred
# format because this path makes process slower in this
# special case
format_is_iso8601 = (
'%Y-%m-%dT%H:%M:%S.%f'.startswith(format) or
'%Y-%m-%d %H:%M:%S.%f'.startswith(format)
)
if format_is_iso8601:
format = None
if format is not None:
# There is a special fast-path for iso8601 formatted
# datetime strings, so in those cases don't use the inferred
# format because this path makes process slower in this
# special case
format_is_iso8601 = (
('%Y-%m-%dT%H:%M:%S.%f'.startswith(format) or
'%Y-%m-%d %H:%M:%S.%f'.startswith(format)) and
format != '%Y'
)
if format_is_iso8601:
require_iso8601 = not infer_datetime_format
format = None

try:
result = None
Expand All @@ -334,16 +337,20 @@ def _convert_listlike(arg, box, format):
raise
result = arg
except ValueError:
# Only raise this error if the user provided the
# datetime format, and not when it was inferred
# if format was inferred, try falling back
# to array_to_datetime - terminate here
# for specified formats
if not infer_datetime_format:
raise
if errors == 'raise':
raise
result = arg

if result is None and (format is None or infer_datetime_format):
result = tslib.array_to_datetime(arg, raise_=errors == 'raise',
result = tslib.array_to_datetime(arg, raise_=errors=='raise',
utc=utc, dayfirst=dayfirst,
yearfirst=yearfirst, freq=freq,
coerce=coerce, unit=unit)
coerce=coerce, unit=unit,
require_iso8601=require_iso8601)

if com.is_datetime64_dtype(result) and box:
result = DatetimeIndex(result, tz='utc' if utc else None)
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16 changes: 14 additions & 2 deletions pandas/tslib.pyx
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Expand Up @@ -1808,7 +1808,8 @@ cpdef object _get_rule_month(object source, object default='DEC'):

cpdef array_to_datetime(ndarray[object] values, raise_=False,
dayfirst=False, yearfirst=False, freq=None,
format=None, utc=None, coerce=False, unit=None):
format=None, utc=None, coerce=False, unit=None,
require_iso8601=False):
cdef:
Py_ssize_t i, n = len(values)
object val, py_dt
Expand Down Expand Up @@ -1908,6 +1909,17 @@ cpdef array_to_datetime(ndarray[object] values, raise_=False,
iresult[i] = value
_check_dts_bounds(&dts)
except ValueError:
# if requiring iso8601 strings, skip trying other formats
if require_iso8601:
if coerce:
iresult[i] = iNaT
continue
elif raise_:
raise ValueError("time data %r does match format specified" %
(val,))
else:
return values

try:
py_dt = parse_datetime_string(val, dayfirst=dayfirst,
yearfirst=yearfirst, freq=freq)
Expand Down Expand Up @@ -1971,7 +1983,7 @@ cpdef array_to_datetime(ndarray[object] values, raise_=False,
continue
try:
oresult[i] = parse_datetime_string(val, dayfirst=dayfirst,
yearfirst=yearfirst, freq=freq)
yearfirst=yearfirst, freq=freq)
_pydatetime_to_dts(oresult[i], &dts)
_check_dts_bounds(&dts)
except Exception:
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4 changes: 4 additions & 0 deletions vb_suite/timeseries.py
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Expand Up @@ -157,6 +157,10 @@ def date_range(start=None, end=None, periods=None, freq=None):
Benchmark('to_datetime(strings)', setup,
start_date=datetime(2012, 7, 11))

timeseries_to_datetime_iso8601_format = \
Benchmark("to_datetime(strings, format='%Y-%m-%d %H:%M:%S')", setup,
start_date=datetime(2012, 7, 11))

setup = common_setup + """
rng = date_range('1/1/2000', periods=10000, freq='D')
strings = Series(rng.year*10000+rng.month*100+rng.day,dtype=np.int64).apply(str)
Expand Down