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import datetime
from timezone_field.backends import get_tz_backend
def normalize_standard(tztuple):
"""Normalize timezone names by replacing special characters with space.
For proper sorting, using spaces makes comparisons more consistent.
:param str tztuple: tuple of timezone and representation
"""
return tztuple[1].translate(str.maketrans({"-": " ", "_": " "}))
def normalize_gmt(tztuple):
"""Normalize timezone GMT names for sorting.
For proper sorting, using GMT values as a positive or negative number.
:param str tztuple: tuple of timezone and representation
"""
gmt = tztuple[1].split()[0]
cmp = gmt.replace("GMT", "").replace(":", "")
return int(cmp)
def standard(timezones):
"""
Given a list of timezones (either strings of timezone objects),
return a list of choices with
* values equal to what was passed in
* display strings as the timezone name without underscores
"""
choices = []
for tz in timezones:
tz_str = str(tz)
choices.append((tz, tz_str.replace("_", " ")))
return sorted(choices, key=normalize_standard)
def with_gmt_offset(timezones, now=None, use_pytz=None):
"""
Given a list of timezones (either strings of timezone objects),
return a list of choices with
* values equal to what was passed in
* display strings formated with GMT offsets and without
underscores. For example: "GMT-05:00 America/New York"
* sorted by their timezone offset
"""
tz_backend = get_tz_backend(use_pytz)
now = now or datetime.datetime.now(tz_backend.utc_tzobj)
_choices = []
for tz in timezones:
tz_str = str(tz)
now_tz = now.astimezone(tz_backend.to_tzobj(tz_str))
delta = now_tz.replace(tzinfo=tz_backend.utc_tzobj) - now
display = "GMT{sign}{gmt_diff} {timezone}".format(
sign="+" if delta == abs(delta) else "-",
gmt_diff=str(abs(delta)).zfill(8)[:-3],
timezone=tz_str.replace("_", " "),
)
_choices.append((delta, tz, display))
_choices.sort(key=lambda x: x[0])
choices = [(one, two) for zero, one, two in _choices]
return sorted(choices, key=normalize_gmt)
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