PERF: rewrited _concat_date_cols function on C with removing extra conversation for integer/float zero and float NaN; rewrited _does_string_look_like_datetime on C

Author: anmyachev

pandas/_libs/tslibs/parsing.pyx

@@ -33,6 +33,8 @@ from dateutil.parser import parse as du_parse
 from pandas._libs.tslibs.ccalendar import MONTH_NUMBERS
 from pandas._libs.tslibs.nattype import nat_strings, NaT
 
+from pandas._libs.datehelpers import _does_string_look_like_datetime
+
 # ----------------------------------------------------------------------
 # Constants
 
@@ -47,8 +49,6 @@ _DEFAULT_DATETIME = datetime(1, 1, 1).replace(hour=0, minute=0,
 cdef:
     object _TIMEPAT = re.compile(r'^([01]?[0-9]|2[0-3]):([0-5][0-9])')
 
-    set _not_datelike_strings = {'a', 'A', 'm', 'M', 'p', 'P', 't', 'T'}
-
 # ----------------------------------------------------------------------
 
 _get_option = None
@@ -187,24 +187,6 @@ cdef parse_datetime_string_with_reso(date_string, freq=None, dayfirst=False,
     return parsed, parsed, reso
 
 
-cpdef bint _does_string_look_like_datetime(object date_string):
-    if date_string.startswith('0'):
-        # Strings starting with 0 are more consistent with a
-        # date-like string than a number
-        return True
-
-    try:
-        if float(date_string) < 1000:
-            return False
-    except ValueError:
-        pass
-
-    if date_string in _not_datelike_strings:
-        return False
-
-    return True
-
-
 cdef inline object _parse_dateabbr_string(object date_string, object default,
                                           object freq):
     cdef: