PERF: parse and timedelta ops improvements, #6755

doc/source/whatsnew/v0.17.0.txt

@@ -54,6 +54,9 @@ Removal of prior version deprecations/changes
 Performance Improvements
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
+- 4x improvement in ``timedelta`` string parsing (:issue:`6755`)
+- 8x improvement in ``timedelta64`` and ``datetime64`` ops (:issue:`6755`)
+
 .. _whatsnew_0170.bug_fixes:
 
 Bug Fixes

pandas/tseries/tests/test_timedeltas.py

@@ -109,6 +109,9 @@ def test_construction(self):
         # currently invalid as it has a - on the hhmmdd part (only allowed on the days)
         self.assertRaises(ValueError, lambda : Timedelta('-10 days -1 h 1.5m 1s 3us'))
 
+        # only leading neg signs are allowed
+        self.assertRaises(ValueError, lambda : Timedelta('10 days -1 h 1.5m 1s 3us'))
+
         # roundtripping both for string and value
         for v in ['1s',
                   '-1s',
@@ -151,7 +154,7 @@ def test_construction(self):
                               "cannot construct a TimeDelta",
                               lambda : Timedelta())
         tm.assertRaisesRegexp(ValueError,
-                              "cannot create timedelta string convert",
+                              "unit abbreviation w/o a number",
                               lambda : Timedelta('foo'))
         tm.assertRaisesRegexp(ValueError,
                               "cannot construct a TimeDelta from the passed arguments, allowed keywords are ",

pandas/tseries/timedeltas.py

@@ -34,22 +34,13 @@ def _convert_listlike(arg, box, unit):
         if isinstance(arg, (list,tuple)) or ((hasattr(arg,'__iter__') and not hasattr(arg,'dtype'))):
             arg = np.array(list(arg), dtype='O')
 
+        # these are shortcutable
         if is_timedelta64_dtype(arg):
             value = arg.astype('timedelta64[ns]')
         elif is_integer_dtype(arg):
-
-            # these are shortcutable
-            value = arg.astype('timedelta64[{0}]'.format(unit)).astype('timedelta64[ns]')
+            value = arg.astype('timedelta64[{0}]'.format(unit)).astype('timedelta64[ns]', copy=False)
         else:
-            try:
-                value = tslib.array_to_timedelta64(_ensure_object(arg), unit=unit, coerce=coerce)
-            except:
-
-                # try to process strings fast; may need to fallback
-                try:
-                    value = np.array([ _get_string_converter(r, unit=unit)() for r in arg ],dtype='m8[ns]')
-                except:
-                    value = np.array([ _coerce_scalar_to_timedelta_type(r, unit=unit, coerce=coerce) for r in arg ])
+            value = tslib.array_to_timedelta64(_ensure_object(arg), unit=unit, coerce=coerce)
             value = value.astype('timedelta64[ns]', copy=False)
 
         if box:
@@ -95,15 +86,6 @@ def _convert_listlike(arg, box, unit):
     'NS' : 'ns',
     'ns' : 'ns',
     }
-_unit_scale = {
-    'd' : 86400*1e9,
-    'h' : 3600*1e9,
-    'm' : 60*1e9,
-    's' : 1e9,
-    'ms' : 1e6,
-    'us' : 1e3,
-    'ns' : 1,
-    }
 
 def _validate_timedelta_unit(arg):
     """ provide validation / translation for timedelta short units """
@@ -114,150 +96,11 @@ def _validate_timedelta_unit(arg):
             return 'ns'
         raise ValueError("invalid timedelta unit {0} provided".format(arg))
 
-_short_search = re.compile(
-    "^\s*(?P<neg>-?)\s*(?P<value>\d*\.?\d*)\s*(?P<unit>d|s|ms|us|ns)?\s*$",re.IGNORECASE)
-_full_search = re.compile(
-    "^\s*(?P<neg>-?)\s*(?P<days>\d*?\.?\d*?)?\s*(days|d|day)?,?\s*\+?(?P<time>\d{1,2}:\d{2}:\d{2})?(?P<frac>\.\d+)?\s*$",re.IGNORECASE)
-_nat_search = re.compile(
-    "^\s*(nat|nan)\s*$",re.IGNORECASE)
-_whitespace = re.compile('^\s*$')
-_number_split = re.compile("^(\d+\.?\d*)")
-
-# construct the full2_search
-abbrevs = [('d' ,'days|d|day'),
-           ('h' ,'hours|h|hour'),
-           ('m' ,'minutes|min|minute|m'),
-           ('s' ,'seconds|sec|second|s'),
-           ('ms','milliseconds|milli|millis|millisecond|ms'),
-           ('us','microseconds|micro|micros|microsecond|us'),
-           ('ns','nanoseconds|nano|nanos|nanosecond|ns')]
-
-_full_search2 = re.compile(''.join(
-    ["^\s*(?P<neg>-?)\s*"] + [ "(?P<" + p + ">\\d+\.?\d*\s*(" + ss + "))?\\s*" for p, ss in abbrevs ] + ['$']))
-
 def _coerce_scalar_to_timedelta_type(r, unit='ns', box=True, coerce=False):
     """ convert strings to timedelta; coerce to Timedelta (if box), else np.timedelta64"""
 
-    if isinstance(r, compat.string_types):
-
-        # we are already converting to nanoseconds
-        converter = _get_string_converter(r, unit=unit)
-        r = converter()
-        unit='ns'
-
     result = tslib.convert_to_timedelta(r,unit,coerce)
     if box:
         result = tslib.Timedelta(result)
 
     return result
-
-def _get_string_converter(r, unit='ns'):
-    """ return a string converter for r to process the timedelta format """
-
-    # treat as a nan
-    if isnull(r):
-        def convert(r=None, unit=None):
-            return tslib.iNaT
-        return convert
-
-    if _whitespace.search(r):
-        def convert(r=None, unit=None):
-            return tslib.iNaT
-        return convert
-
-    m = _short_search.search(r)
-    if m:
-        def convert(r=None, unit=unit, m=m):
-            if r is not None:
-                m = _short_search.search(r)
-
-            gd = m.groupdict()
-
-            r = float(gd['value'])
-            u = gd.get('unit')
-            if u is not None:
-                unit = u.lower()
-            result = tslib.cast_from_unit(r, unit)
-            if gd['neg']:
-                result *= -1
-            return result
-        return convert
-
-    m = _full_search.search(r)
-    if m:
-        def convert(r=None, unit=None, m=m):
-            if r is not None:
-                m = _full_search.search(r)
-
-            gd = m.groupdict()
-
-            # handle time
-            value = 0
-            time = gd['time']
-            if time:
-                (hh,mm,ss) = time.split(':')
-                value += int((float(hh)*3600 + float(mm)*60 + float(ss))*1e9)
-
-            # handle frac
-            frac = gd['frac']
-            if frac:
-                value += round(float(frac)*1e9)
-
-            # handle days (possibly negative)
-            is_neg = gd['neg']
-            if gd['days']:
-                days = int((float(gd['days'] or 0) * 86400)*1e9)
-                if is_neg:
-                    days *= -1
-                value += days
-            else:
-                if is_neg:
-                    value *= -1
-            return tslib.cast_from_unit(value, 'ns')
-        return convert
-
-    # look for combo strings
-    m = _full_search2.search(r)
-    if m:
-        def convert(r=None, unit=None, m=m):
-            if r is not None:
-                m = _full_search2.search(r)
-
-            gd = m.groupdict()
-
-            # the parser
-            def parse(k, v):
-                if v is None:
-                    return 0
-                v = float(_number_split.search(v).group())
-                return int(v*_unit_scale[k])
-
-            # handle non-days
-            days = gd.pop('days',None)
-            neg = gd.pop('neg',None)
-            value = 0
-            for k, v in gd.items():
-                value += parse(k,v)
-
-            # parse days / neg
-            if days:
-                days = parse('days',days)
-                if neg:
-                    days *= -1
-                value += days
-            else:
-                if neg:
-                    value *= -1
-
-            return tslib.cast_from_unit(value, 'ns')
-        return convert
-
-    m = _nat_search.search(r)
-    if m:
-        def convert(r=None, unit=None, m=m):
-            return tslib.iNaT
-        return convert
-
-    # no converter
-    raise ValueError("cannot create timedelta string converter for [{0}]".format(r))
-

pandas/tseries/tools.py

@@ -263,6 +263,7 @@ def _convert_listlike(arg, box, format):
         if isinstance(arg, (list,tuple)):
             arg = np.array(arg, dtype='O')
 
+        # these are shortcutable
         if com.is_datetime64_ns_dtype(arg):
             if box and not isinstance(arg, DatetimeIndex):
                 try:
@@ -271,6 +272,12 @@ def _convert_listlike(arg, box, format):
                     pass
 
             return arg
+        elif format is None and com.is_integer_dtype(arg) and unit=='ns':
+            result = arg.astype('datetime64[ns]')
+            if box:
+                return DatetimeIndex(result, tz='utc' if utc else None)
+
+            return result
 
         arg = com._ensure_object(arg)