simple_specification
A simple pythonic implementation of the Specification Pattern for Python 3.7 or higher.
Installation
pip install simple-specification
Examples
Creating specification classes to check integer numbers
from simple_specification import Specification
# hardcoded specification
class Odd(Specification):
def is_satisfied_by(self, candidate: int) -> bool:
return candidate % 2 != 0
# parametrized specification
class DivisibleBy(Specification):
def __init__(self, number: int):
self.number = number
def is_satisfied_by(self, candidate: int) -> bool:
return candidate % self.number == 0
Instantiating the specifications
>>> odd = Odd()
>>> even = ~odd
>>> div3 = DivisibleBy(3)
>>> div5 = DivisibleBy(5)
is_satisfied_by(candidate)
Using specifications - method >>> odd.is_satisfied_by(1)
True
>>> odd.is_satisfied_by(2)
False
>>> even.is_satisfied_by(3)
False
>>> even.is_satisfied_by(4)
True
>>> div3.is_satisfied_by(9)
True
>>> div5.is_satisfied_by(12)
False
&
and |
Composing specifications - operators >>> # AND
>>> (even & div3).is_satisfied_by(6)
True
>>> (even & div3).is_satisfied_by(9)
False
>>> (even & div3 & div5).is_satisfied_by(30)
True
>>> (even & div3 & div5).is_satisfied_by(36)
False
>>>
>>> # OR
>>> (even | div3).is_satisfied_by(10)
True
>>> (even | div3).is_satisfied_by(15)
True
>>> (even | div3).is_satisfied_by(5)
False
~
Negating specifications - operator Warning
Always surround the negation with parenthesis
>>> (~odd).is_satisfied_by(2)
True
>>> (~div5).is_satisfied_by(25)
False
>>> (~div5).is_satisfied_by(11)
True
>>> (~(odd | div5)).is_satisfied_by(6)
True
>>> (~(odd | div5)).is_satisfied_by(7)
False
&
- class method Specification.all(specs)
Composing a list of specifications with >>> all_spec = Specification.all([~even, div3, div5])
>>> all_spec.is_satisfied_by(15)
True
>>> all_spec.is_satisfied_by(30)
False
>>> all_spec.is_satisfied_by(25)
False
>>> all_spec.is_satisfied_by(6)
False
|
- class method Specification.any(specs)
Composing a list of specifications with >>> div15 = DivisibleBy(3) & DivisibleBy(5)
>>> any_spec = Specification.any([div15, even])
>>> any_spec.is_satisfied_by(2)
True
>>> any_spec.is_satisfied_by(15)
True
>>> any_spec.is_satisfied_by(30)
True
>>> any_spec.is_satisfied_by(3)
False
>>> any_spec.is_satisfied_by(5)
False