There are no ABCs for ordering operations. This is because the recursive class difinition like:
class Derived(XXX(Derived)):
is invalid syntax. This recipe implements an ABC ordering class with using decorator.
Python, 46 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | import abc
def keycomparable(Derived):
class KeyComparableImpl(metaclass = abc.ABCMeta):
@abc.abstractmethod
def _cmpkey(self):
pass
def __lt__(self, other):
if not isinstance(other, Derived):
return NotImplemented
return self._cmpkey() < other._cmpkey()
def __le__(self, other):
if not isinstance(other, Derived):
return NotImplemented
return self._cmpkey() <= other._cmpkey()
def __eq__(self, other):
if not isinstance(other, Derived):
return NotImplemented
return self._cmpkey() == other._cmpkey()
class Wrapper(Derived, KeyComparableImpl):
pass
Wrapper.__name__ = Derived.__name__
Wrapper.__doc__ = Derived.__doc__
return Wrapper
@keycomparable
class IntABS:
"sample class"
def __init__(self,val):
self.val = val
def _cmpkey(self):
return abs(self.val)
def __str__(self):
return str(abs(self.val))
def __repr__(self):
return "abs({0})".format(self.val)
|
