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@aodin aodin/quarter.py
Last active Sep 23, 2018

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Python 3 datetime.date subclass
import copy
import datetime
import pickle
# Each quarter corresponds to the following month and day combinations:
_q1 = (3, 31)
_q2 = (6, 30)
_q3 = (9, 30)
_q4 = (12, 31)
_qs = [_q1, _q2, _q3, _q4]
class Quarter(datetime.date):
def __new__(cls, year, q):
if q < 1 or q > 4:
raise ValueError("Quarter must be 1, 2, 3 or 4")
month, day = _qs[q-1]
return super().__new__(cls, year, month, day)
@property
def q(self):
return self.month // 3 # We want an int type
def __repr__(self):
return '{0}({1}, {2})'.format(self.__class__.__name__, self.year, self.q)
def __reduce__(self):
return (self.__class__, (self.year, self.q))
# Some example magic methods
def __str__(self):
return "{year} Q{q}".format(year=self.year, q=self.q)
def __add__(self, other):
"""Add an integer number of quarters to the existing quarter."""
assert isinstance(other, int)
value = self.year * 4 + self.q + other - 1
return Quarter(value // 4, value % 4 + 1)
if __name__ == '__main__':
q1 = Quarter(2018, 1)
assert eval(repr(q1)) == q1
# Copy
assert isinstance(copy.copy(q1), Quarter)
assert copy.copy(q1) == q1
# Pickle
assert isinstance(pickle.loads(pickle.dumps(q1)), Quarter)
assert pickle.loads(pickle.dumps(q1)) == q1
# Hashing
quarters = {q1: True}
assert quarters[q1]
# Other methods
assert q1 < Quarter(2018, 2)
assert q1 <= Quarter(2018, 1)
assert q1 > Quarter(2017, 4)
assert str(q1) == "2018 Q1"
assert (q1 + 3) == Quarter(2018, 4)
assert (q1 + 4) == Quarter(2019, 1)
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