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"""
Defines lookup classes to be used in ResultSet's filter method.
"""
from . import utilities
registry = {}
class Registrar(type):
"""
A lookup class that implements this metaclass, i.e. all lookup classes that inherit from
Lookup, will be added to a lookup registry to be used in ResultSet's filter method. Lookup
class, at minimum, should define a lookup_name attribute and implement a __call__ method,
otherwise it will be considered a base class and won't be added to the registry.
"""
def __new__(mcs, name, bases, attrs):
cls = super(Registrar, mcs).__new__(mcs, name, bases, attrs)
if attrs['lookup_name'] is None: # base classes shouldn't be added to the registry
return cls
registry[attrs['lookup_name']] = cls()
return cls
class Lookup(utilities.with_metaclass(Registrar)):
lookup_name = None
def __call__(self, resource_value, requested_value):
raise NotImplementedError
class Exact(Lookup):
lookup_name = 'exact'
def __call__(self, resource_value, requested_value):
return resource_value == requested_value
class In(Lookup):
lookup_name = 'in'
def __call__(self, resource_value, requested_values):
return resource_value in requested_values
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