Hand written ISO parser for Timedelta construction

Author: WillAyd

pandas/_libs/tslibs/timedeltas.pyx

@@ -1,7 +1,6 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
 import collections
-import re
 
 import sys
 cdef bint PY3 = (sys.version_info[0] >= 3)
@@ -236,6 +235,14 @@ cpdef inline int64_t cast_from_unit(object ts, object unit) except? -1:
  return <int64_t> (base *m) + <int64_t> (frac *m)
 
 
+cdef inline _decode_if_necessary(object ts):
+ # decode ts if necessary
+ if not PyUnicode_Check(ts) and not PY3:
+ ts = str(ts).decode('utf-8')
+
+ return ts
+
+
 cdef inline parse_timedelta_string(object ts):
  """
  Parse a regular format timedelta string. Return an int64_t (in ns)
@@ -258,9 +265,7 @@ cdef inline parse_timedelta_string(object ts):
  if len(ts) == 0 or ts in nat_strings:
  return NPY_NAT
 
- # decode ts if necessary
- if not PyUnicode_Check(ts) and not PY3:
- ts = str(ts).decode('utf-8')
+ ts = _decode_if_necessary(ts)
 
  for c in ts:
 
@@ -507,26 +512,14 @@ def _binary_op_method_timedeltalike(op, name):
 # ----------------------------------------------------------------------
 # Timedelta Construction
 
-iso_pater = re.compile(r"""P
- (?P<days>-?[0-9]*)DT
- (?P<hours>[0-9]{1,2})H
- (?P<minutes>[0-9]{1,2})M
- (?P<seconds>[0-9]{0,2})
- (\.
- (?P<milliseconds>[0-9]{1,3})
- (?P<microseconds>[0-9]{0,3})
- (?P<nanoseconds>[0-9]{0,3})
- )?S""", re.VERBOSE)
-
-
-cdef int64_t parse_iso_format_string(object iso_fmt) except? -1:
+cdef inline int64_t parse_iso_format_string(object ts) except? -1:
  """
  Extracts and cleanses the appropriate values from a match object with
  groups for each component of an ISO 8601 duration
 
  Parameters
  ----------
- iso_fmt:
+ ts:
  ISO 8601 Duration formatted string
 
  Returns
@@ -537,25 +530,93 @@ cdef int64_t parse_iso_format_string(object iso_fmt) except? -1:
  Raises
  ------
  ValueError
- If ``iso_fmt`` cannot be parsed
+ If ``ts`` cannot be parsed
  """
 
- cdef int64_t ns = 0
+ cdef:
+ unicode c
+ int64_t result = 0, r
+ int p=0
+ object dec_unit = 'ms', err_msg
+ bint have_dot=0, have_value=0, neg=0
+ list number=[], unit=[]
 
- match = re.match(iso_pater, iso_fmt)
- if match:
- match_dict = match.groupdict(default='0')
- for comp in ['milliseconds', 'microseconds', 'nanoseconds']:
- match_dict[comp] = '{:0<3}'.format(match_dict[comp])
+ ts = _decode_if_necessary(ts)
 
- for k, v in match_dict.items():
- ns += timedelta_from_spec(v, '0', k)
+ err_msg = "Invalid ISO 8601 Duration format - {}".format(ts)
 
- else:
- raise ValueError("Invalid ISO 8601 Duration format - "
- "{}".format(iso_fmt))
+ for c in ts:
+ # number (ascii codes)
+ if ord(c) >= 48 and ord(c) <= 57:
+
+ have_value = 1
+ if have_dot:
+ if p == 3 and dec_unit != 'ns':
+ unit.append(dec_unit)
+ if dec_unit == 'ms':
+ dec_unit = 'us'
+ elif dec_unit == 'us':
+ dec_unit = 'ns'
+ p = 0
+ p += 1
+
+ if not len(unit):
+ number.append(c)
+ else:
+ # if in days, pop trailing T
+ if unit[-1] == 'T':
+ unit.pop()
+ elif 'H' in unit or 'M' in unit:
+ if len(number) > 2:
+ raise ValueError(err_msg)
+ r = timedelta_from_spec(number, '0', unit)
+ result += timedelta_as_neg(r, neg)
 
- return ns
+ neg = 0
+ unit, number = [], [c]
+ else:
+ if c == 'P':
+ pass # ignore leading character
+ elif c == '-':
+ if neg or have_value:
+ raise ValueError(err_msg)
+ else:
+ neg = 1
+ elif c in ['D', 'T', 'H', 'M']:
+ unit.append(c)
+ elif c == '.':
+ # append any seconds
+ if len(number):
+ r = timedelta_from_spec(number, '0', 'S')
+ result += timedelta_as_neg(r, neg)
+ unit, number = [], []
+ have_dot = 1
+ elif c == 'S':
+ if have_dot: # ms, us, or ns
+ if not len(number) or p > 3:
+ raise ValueError(err_msg)
+ # pad to 3 digits as required
+ pad = 3 - p
+ while pad > 0:
+ number.append('0')
+ pad -= 1
+
+ r = timedelta_from_spec(number, '0', dec_unit)
+ result += timedelta_as_neg(r, neg)
+ else: # seconds
+ if len(number) <= 2:
+ r = timedelta_from_spec(number, '0', 'S')
+ result += timedelta_as_neg(r, neg)
+ else:
+ raise ValueError(err_msg)
+ else:
+ raise ValueError(err_msg)
+
+ if not have_value:
+ # Received string only - never parsed any values
+ raise ValueError(err_msg)
+
+ return result
 
 
 cdef _to_py_int_float(v):