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"""
This modules provides a method to parse an ISO 8601:2004 time string to a
Python datetime.time instance.
It supports all basic and extended formats including time zone specifications
as described in the ISO standard.
"""
import re
from decimal import Decimal, ROUND_FLOOR
from datetime import time
from isodate.isostrf import strftime, TIME_EXT_COMPLETE, TZ_EXT
from isodate.isoerror import ISO8601Error
from isodate.isotzinfo import TZ_REGEX, build_tzinfo
TIME_REGEX_CACHE = []
# used to cache regular expressions to parse ISO time strings.
def build_time_regexps():
"""
Build regular expressions to parse ISO time string.
The regular expressions are compiled and stored in TIME_REGEX_CACHE
for later reuse.
"""
if not TIME_REGEX_CACHE:
# ISO 8601 time representations allow decimal fractions on least
# significant time component. Command and Full Stop are both valid
# fraction separators.
# The letter 'T' is allowed as time designator in front of a time
# expression.
# Immediately after a time expression, a time zone definition is
# allowed.
# a TZ may be missing (local time), be a 'Z' for UTC or a string of
# +-hh:mm where the ':mm' part can be skipped.
# TZ information patterns:
# ''
# Z
# +-hh:mm
# +-hhmm
# +-hh =>
# isotzinfo.TZ_REGEX
def add_re(regex_text):
TIME_REGEX_CACHE.append(re.compile(r"\A" + regex_text + TZ_REGEX + r"\Z"))
# 1. complete time:
# hh:mm:ss.ss ... extended format
add_re(
r"T?(?P<hour>[0-9]{2}):"
r"(?P<minute>[0-9]{2}):"
r"(?P<second>[0-9]{2}"
r"([,.][0-9]+)?)"
)
# hhmmss.ss ... basic format
add_re(
r"T?(?P<hour>[0-9]{2})"
r"(?P<minute>[0-9]{2})"
r"(?P<second>[0-9]{2}"
r"([,.][0-9]+)?)"
)
# 2. reduced accuracy:
# hh:mm.mm ... extended format
add_re(r"T?(?P<hour>[0-9]{2}):" r"(?P<minute>[0-9]{2}" r"([,.][0-9]+)?)")
# hhmm.mm ... basic format
add_re(r"T?(?P<hour>[0-9]{2})" r"(?P<minute>[0-9]{2}" r"([,.][0-9]+)?)")
# hh.hh ... basic format
add_re(r"T?(?P<hour>[0-9]{2}" r"([,.][0-9]+)?)")
return TIME_REGEX_CACHE
def parse_time(timestring):
"""
Parses ISO 8601 times into datetime.time objects.
Following ISO 8601 formats are supported:
(as decimal separator a ',' or a '.' is allowed)
hhmmss.ssTZD basic complete time
hh:mm:ss.ssTZD extended compelte time
hhmm.mmTZD basic reduced accuracy time
hh:mm.mmTZD extended reduced accuracy time
hh.hhTZD basic reduced accuracy time
TZD is the time zone designator which can be in the following format:
no designator indicates local time zone
Z UTC
+-hhmm basic hours and minutes
+-hh:mm extended hours and minutes
+-hh hours
"""
isotimes = build_time_regexps()
for pattern in isotimes:
match = pattern.match(timestring)
if match:
groups = match.groupdict()
for key, value in groups.items():
if value is not None:
groups[key] = value.replace(",", ".")
tzinfo = build_tzinfo(
groups["tzname"],
groups["tzsign"],
int(groups["tzhour"] or 0),
int(groups["tzmin"] or 0),
)
if "second" in groups:
second = Decimal(groups["second"]).quantize(
Decimal(".000001"), rounding=ROUND_FLOOR
)
microsecond = (second - int(second)) * int(1e6)
# int(...) ... no rounding
# to_integral() ... rounding
return time(
int(groups["hour"]),
int(groups["minute"]),
int(second),
int(microsecond.to_integral()),
tzinfo,
)
if "minute" in groups:
minute = Decimal(groups["minute"])
second = Decimal((minute - int(minute)) * 60).quantize(
Decimal(".000001"), rounding=ROUND_FLOOR
)
microsecond = (second - int(second)) * int(1e6)
return time(
int(groups["hour"]),
int(minute),
int(second),
int(microsecond.to_integral()),
tzinfo,
)
else:
microsecond, second, minute = 0, 0, 0
hour = Decimal(groups["hour"])
minute = (hour - int(hour)) * 60
second = (minute - int(minute)) * 60
microsecond = (second - int(second)) * int(1e6)
return time(
int(hour),
int(minute),
int(second),
int(microsecond.to_integral()),
tzinfo,
)
raise ISO8601Error("Unrecognised ISO 8601 time format: %r" % timestring)
def time_isoformat(ttime, format=TIME_EXT_COMPLETE + TZ_EXT):
"""
Format time strings.
This method is just a wrapper around isodate.isostrf.strftime and uses
Time-Extended-Complete with extended time zone as default format.
"""
return strftime(ttime, format)
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