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179 lines
3.3 KiB
179 lines
3.3 KiB
# -*- coding: utf-8 -*-
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"""
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Provides the AccountingNone singleton
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AccountingNone is a null value that dissolves in basic arithmetic operations,
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as illustrated in the examples below. In comparisons, AccountingNone behaves
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the same as zero.
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>>> 1 + 1
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2
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>>> 1 + AccountingNone
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1
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>>> AccountingNone + 1
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1
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>>> AccountingNone + None
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AccountingNone
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>>> +AccountingNone
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AccountingNone
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>>> -AccountingNone
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AccountingNone
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>>> -(AccountingNone)
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AccountingNone
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>>> AccountingNone - 1
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-1
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>>> 1 - AccountingNone
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1
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>>> AccountingNone - None
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AccountingNone
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>>> AccountingNone / 2
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0.0
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>>> 2 / AccountingNone
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Traceback (most recent call last):
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...
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ZeroDivisionError
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>>> AccountingNone / AccountingNone
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AccountingNone
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>>> AccountingNone // 2
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0.0
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>>> 2 // AccountingNone
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Traceback (most recent call last):
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...
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ZeroDivisionError
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>>> AccountingNone // AccountingNone
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AccountingNone
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>>> AccountingNone * 2
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0.0
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>>> 2 * AccountingNone
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0.0
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>>> AccountingNone * AccountingNone
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AccountingNone
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>>> AccountingNone * None
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AccountingNone
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>>> None * AccountingNone
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AccountingNone
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>>> str(AccountingNone)
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''
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>>> bool(AccountingNone)
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False
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>>> AccountingNone > 0
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False
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>>> AccountingNone < 0
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False
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>>> AccountingNone < 1
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True
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>>> AccountingNone > 1
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False
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>>> 0 < AccountingNone
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False
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>>> 0 > AccountingNone
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False
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>>> 1 < AccountingNone
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False
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>>> 1 > AccountingNone
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True
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>>> AccountingNone == 0
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True
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>>> AccountingNone == 0.0
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True
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>>> AccountingNone == None
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True
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"""
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class AccountingNoneType(object):
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def __add__(self, other):
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if other is None:
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return AccountingNone
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return other
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__radd__ = __add__
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def __sub__(self, other):
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if other is None:
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return AccountingNone
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return -other
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def __rsub__(self, other):
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if other is None:
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return AccountingNone
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return other
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def __iadd__(self, other):
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if other is None:
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return AccountingNone
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return other
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def __isub__(self, other):
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if other is None:
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return AccountingNone
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return -other
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def __pos__(self):
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return self
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def __neg__(self):
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return self
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def __div__(self, other):
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if other is AccountingNone:
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return AccountingNone
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return 0.0
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def __rdiv__(self, other):
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raise ZeroDivisionError
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def __floordiv__(self, other):
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if other is AccountingNone:
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return AccountingNone
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return 0.0
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def __rfloordiv__(self, other):
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raise ZeroDivisionError
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def __truediv__(self, other):
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if other is AccountingNone:
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return AccountingNone
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return 0.0
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def __rtruediv__(self, other):
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raise ZeroDivisionError
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def __mul__(self, other):
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if other is None or other is AccountingNone:
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return AccountingNone
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return 0.0
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__rmul__ = __mul__
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def __repr__(self):
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return 'AccountingNone'
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def __str__(self):
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return ''
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def __nonzero__(self):
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return False
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def __bool__(self):
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return False
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def __eq__(self, other):
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return other == 0 or other is None or other is AccountingNone
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def __lt__(self, other):
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return 0 < other
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def __gt__(self, other):
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return 0 > other
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AccountingNone = AccountingNoneType()
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if __name__ == '__main__':
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import doctest
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doctest.testmod()
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