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Fix negative timedelta parsing to match timedelta.__str__ semantics (fixes #23) #41

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Fix negative timedelta parsing to match timedelta.__str__ semantics (fixes #23) #41

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30 changes: 28 additions & 2 deletions pytimeparse/tests/testtimeparse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -240,16 +240,42 @@ def test_timeparse_11(self):
# uptime format
self.assertEqual(timeparse.timeparse("2 days, 4:13:02"), 187982)
self.assertEqual(timeparse.timeparse("+2 days, 4:13:02"), 187982)
self.assertEqual(timeparse.timeparse("-2 days, 4:13:02"), -187982)
# A leading minus negates only the day count, matching the semantics
# of timedelta.__str__ (the HH:MM:SS clock stays non-negative).
self.assertEqual(timeparse.timeparse("-2 days, 4:13:02"), -157618)

def test_timeparse_12(self):
"""timeparse test case 12."""
self.assertAlmostEqual(timeparse.timeparse("2 days, 4:13:02.266"), 187982.266)
self.assertAlmostEqual(timeparse.timeparse("+2 days, 4:13:02.266"), 187982.266)
self.assertAlmostEqual(
timeparse.timeparse("-2 days, 4:13:02.266"), -187982.266
timeparse.timeparse("-2 days, 4:13:02.266"), -157617.734
)

def test_negative_day_clock(self):
"""A leading minus applies only to the day count (issue #23)."""
self.assertEqual(timeparse.timeparse("-1 day, 0:00:05"), -86395)
self.assertEqual(timeparse.timeparse("-2 days, 4:13:02"), -157618)
self.assertAlmostEqual(
timeparse.timeparse("-1 day, 0:00:14.513431"), -86385.486569
)

def test_negative_timedelta_roundtrip(self):
"""timeparse inverts timedelta.__str__ without drift (issue #23)."""
from datetime import timedelta

for td in [
timedelta(days=-1, seconds=5),
timedelta(days=-3, seconds=71218),
timedelta(seconds=-86395),
timedelta(days=-1, microseconds=14513431),
]:
with self.subTest(td=td):
text = str(td)
self.assertAlmostEqual(
timeparse.timeparse(text), td.total_seconds(), places=6, msg=text
)

def test_timeparse_13(self):
"""timeparse test case 13."""
self.assertEqual(timeparse.timeparse("5hr34m56s"), 20096)
Expand Down
79 changes: 39 additions & 40 deletions pytimeparse/timeparse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -122,6 +122,31 @@ def _interpret_as_minutes(
return mdict


def _sum_fields(mdict: dict[str, Optional[str]], sign: int) -> Union[int, float]:
"""
Sum the seconds represented by parsed fields, applying ``sign``.

Returns an ``int`` when the result is a whole number of seconds and a
``float`` otherwise.
"""
values = [(k, v) for k, v in mdict.items() if v is not None]
# if all of the fields are integer numbers
if all(v.isdigit() for _, v in values):
return sign * sum(MULTIPLIERS[k] * int(v, 10) for k, v in values)
secs = mdict.get("secs")
# if SECS is an integer number (or absent)
if secs is None or secs.isdigit():
# we will return an integer
return sign * (
# sum exactly so that values such as '4.1m' are
# not truncated one second short by float error
int(sum(MULTIPLIERS[k] * Decimal(v) for k, v in values if k != "secs"))
+ (int(secs, 10) if secs else 0)
)
# SECS is a float, we will return a float
return sign * sum(MULTIPLIERS[k] * float(v) for k, v in values)


def timeparse(sval: str, granularity: str = "seconds") -> Optional[Union[int, float]]:
"""
Parse a time expression, returning it as a number of seconds. If
Expand Down Expand Up @@ -165,52 +190,26 @@ def timeparse(sval: str, granularity: str = "seconds") -> Optional[Union[int, fl
assert match is not None
sign = -1 if match.groupdict()["sign"] == "-" else 1
sval = match.groupdict()["unsigned"]
for timefmt in COMPILED_TIMEFORMATS:
for idx, timefmt in enumerate(COMPILED_TIMEFORMATS):
match = timefmt.match(sval)
if match and match.group(0).strip():
mdict = match.groupdict()
if granularity == "minutes":
mdict = _interpret_as_minutes(sval, mdict)
try:
# if all of the fields are integer numbers
if all(v.isdigit() for v in list(mdict.values()) if v):
return sign * sum(
[
MULTIPLIERS[k] * int(v, 10)
for (k, v) in list(mdict.items())
if v is not None
]
)
# if SECS is an integer number
elif (
"secs" not in mdict
or mdict["secs"] is None
or mdict["secs"].isdigit()
):
# we will return an integer
return sign * (
# sum exactly so that values such as '4.1m' are
# not truncated one second short by float error
int(
sum(
[
MULTIPLIERS[k] * Decimal(v)
for (k, v) in list(mdict.items())
if k != "secs" and v is not None
]
)
)
+ (int(mdict["secs"], 10) if mdict["secs"] else 0)
)
else:
# SECS is a float, we will return a float
return sign * sum(
[
MULTIPLIERS[k] * float(v)
for (k, v) in list(mdict.items())
if v is not None
]
)
# `datetime.timedelta.__str__` renders negative durations as
# "-N day[s], HH:MM:SS[.ffffff]": the leading minus applies
# only to the day/week portion while the clock part stays
# non-negative. Pattern 2 (weeks/days followed by an
# HH:MM:SS clock) is that form; DAYCLOCK (pattern 3) is not.
day_clock = idx == 2 and mdict.get("days") is not None
if day_clock and sign == -1:
date_mdict = {k: mdict.get(k) for k in ("weeks", "days")}
clock_mdict = {
k: v for k, v in mdict.items() if k not in ("weeks", "days")
}
return _sum_fields(date_mdict, -1) + _sum_fields(clock_mdict, 1)
return _sum_fields(mdict, sign)
except (ValueError, InvalidOperation):
# Malformed number string (e.g. '1.2.3', '.') — skip to
# the next time format pattern per documented behavior.
Expand Down