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GeezerVison is showing github.com — python-patterns/specification.py at master · phoosiangchuen/python-patterns

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
@author: Gordeev Andrey <[email protected]>
Specification provide recombination business logic by
chaining together using boolean logic
"""
from abc import abstractmethod
class Specification(object):
def and_specification(self, candidate):
raise NotImplementedError()
def or_specification(self, candidate):
raise NotImplementedError()
def not_specification(self):
raise NotImplementedError()
@abstractmethod
def is_satisfied_by(self, candidate):
pass
class CompositeSpecification(Specification):
@abstractmethod
def is_satisfied_by(self, candidate):
pass
def and_specification(self, candidate):
return AndSpecification(self, candidate)
def or_specification(self, candidate):
return OrSpecification(self, candidate)
def not_specification(self):
return NotSpecification(self)
class AndSpecification(CompositeSpecification):
_one = Specification()
_other = Specification()
def __init__(self, one, other):
self._one = one
self._other = other
def is_satisfied_by(self, candidate):
return bool(self._one.is_satisfied_by(candidate) and
self._other.is_satisfied_by(candidate))
class OrSpecification(CompositeSpecification):
_one = Specification()
_other = Specification()
def __init__(self, one, other):
self._one = one
self._other = other
def is_satisfied_by(self, candidate):
return bool(self._one.is_satisfied_by(candidate) or
self._other.is_satisfied_by(candidate))
class NotSpecification(CompositeSpecification):
_wrapped = Specification()
def __init__(self, wrapped):
self._wrapped = wrapped
def is_satisfied_by(self, candidate):
return bool(not self._wrapped.is_satisfied_by(candidate))
class User(object):
def __init__(self, super_user=False):
self.super_user = super_user
class UserSpecification(CompositeSpecification):
def is_satisfied_by(self, candidate):
return isinstance(candidate, User)
class SuperUserSpecification(CompositeSpecification):
def is_satisfied_by(self, candidate):
return getattr(candidate, 'super_user', False)
if __name__ == '__main__':
print('Specification')
andrey = User()
ivan = User(super_user=True)
vasiliy = 'not User instance'
root_specification = UserSpecification().\
and_specification(SuperUserSpecification())
print(root_specification.is_satisfied_by(andrey))
print(root_specification.is_satisfied_by(ivan))
print(root_specification.is_satisfied_by(vasiliy))
### OUTPUT ###
# Specification
# False
# True
# False
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