Created
October 31, 2019 12:25
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Play around with a hashable and comparable object in python
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| #!/usr/bin/env python3 | |
| class mE(): | |
| def __init__(self, value): | |
| self.v = value | |
| # we need __hash__ and __eq__ for the set | |
| def __hash__(self): | |
| # the maximum length of hash is restricted by the platform: | |
| # https://docs.python.org/3/reference/datamodel.html#object.__hash__ | |
| # if the string exceeds this length we need to do: | |
| # return hash(ord(self.v.lower())) | |
| return ord(self.v.lower()) | |
| def __eq__(self, other): | |
| return hash(self) == hash(other) | |
| # we need __lt__ and __le__ for the object to be comparable | |
| def __lt__(self, other): | |
| return hash(self) < hash(other) | |
| def __le__(self, other): | |
| return hash(self) <= hash(other) | |
| # if __lt__ and __le__ are implemented __gt__ and __ge__ are optional | |
| # def __gt__(self, other): | |
| # return hash(self) > hash(other) | |
| # | |
| # def __ge__(self, other): | |
| # return hash(self) >= hash(other) | |
| # we need __str__ when str() or print() is called | |
| def __str__(self): | |
| return self.v | |
| # we need __repr__() when the set is printed that contains instances | |
| def __repr__(self): | |
| return "mE(v: '{}')".format(self.v) | |
| a = set([mE('A'), mE('a'), mE('b'), mE('c'), mE('D'), mE('d')]) | |
| b = set([mE('A'), mE('B')]) | |
| print(mE('A') != mE('a')) | |
| print(mE('A') != mE('B')) | |
| print(mE('A') < mE('B')) | |
| print(mE('A') > mE('B')) | |
| print(mE('A') <= mE('B')) | |
| print(mE('A') >= mE('B')) | |
| print(mE('A')) | |
| print(mE('a')) | |
| print(sorted(a)) | |
| print(sorted(a-b)) |
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