95 lines
3.1 KiB
Python
95 lines
3.1 KiB
Python
|
class AbstractMethod (object):
|
||
|
|
"""Defines a class to create abstract methods
|
||
|
|
|
||
|
|
@example:
|
||
|
|
class Foo:
|
||
|
|
foo = AbstractMethod('foo')
|
||
|
|
"""
|
||
|
|
def __init__(self, func):
|
||
|
|
"""Constructor
|
||
|
|
|
||
|
|
@params func: name of the function (used when raising an
|
||
|
|
exception).
|
||
|
|
@type func: str
|
||
|
|
"""
|
||
|
|
self._function = func
|
||
|
|
|
||
|
|
def __get__(self, obj, type):
|
||
|
|
"""Get callable object
|
||
|
|
|
||
|
|
@returns An instance of AbstractMethodHelper.
|
||
|
|
|
||
|
|
This trickery is needed to get the name of the class for which
|
||
|
|
an abstract method was requested, otherwise it would be
|
||
|
|
sufficient to include a __call__ method in the AbstractMethod
|
||
|
|
class itself.
|
||
|
|
"""
|
||
|
|
return self.AbstractMethodHelper(self._function, type)
|
||
|
|
|
||
|
|
class AbstractMethodHelper (object):
|
||
|
|
"""Abstract method helper class
|
||
|
|
|
||
|
|
An AbstractMethodHelper instance is a callable object that
|
||
|
|
represents an abstract method.
|
||
|
|
"""
|
||
|
|
def __init__(self, func, cls):
|
||
|
|
self._function = func
|
||
|
|
self._class = cls
|
||
|
|
|
||
|
|
def __call__(self, *args, **kwargs):
|
||
|
|
"""Call abstract method
|
||
|
|
|
||
|
|
Raises a TypeError, because abstract methods can not be
|
||
|
|
called.
|
||
|
|
"""
|
||
|
|
raise TypeError('Abstract method `' + self._class.__name__ \
|
||
|
|
+ '.' + self._function + '\' called')
|
||
|
|
|
||
|
|
|
||
|
|
class Metaclass (type):
|
||
|
|
def __init__(cls, name, bases, *args, **kwargs):
|
||
|
|
"""Configure a new class
|
||
|
|
|
||
|
|
@param cls: Class object
|
||
|
|
@param name: Name of the class
|
||
|
|
@param bases: All base classes for cls
|
||
|
|
"""
|
||
|
|
super(Metaclass, cls).__init__(cls, name, bases, *args, **kwargs)
|
||
|
|
|
||
|
|
# Detach cls.new() from class Metaclass, and make it a method
|
||
|
|
# of cls.
|
||
|
|
cls.__new__ = staticmethod(cls.new)
|
||
|
|
|
||
|
|
# Find all abstract methods, and assign the resulting list to
|
||
|
|
# cls.__abstractmethods__, so we can read that variable when a
|
||
|
|
# request for allocation (__new__) is done.
|
||
|
|
abstractmethods = []
|
||
|
|
ancestors = list(cls.__mro__)
|
||
|
|
ancestors.reverse() # Start with __builtin__.object
|
||
|
|
for ancestor in ancestors:
|
||
|
|
for clsname, clst in ancestor.__dict__.items():
|
||
|
|
if isinstance(clst, AbstractMethod):
|
||
|
|
abstractmethods.append(clsname)
|
||
|
|
else:
|
||
|
|
if clsname in abstractmethods:
|
||
|
|
abstractmethods.remove(clsname)
|
||
|
|
|
||
|
|
abstractmethods.sort()
|
||
|
|
setattr(cls, '__abstractmethods__', abstractmethods)
|
||
|
|
|
||
|
|
def new(self, cls):
|
||
|
|
"""Allocator for class cls
|
||
|
|
|
||
|
|
@param self: Class object for which an instance should be
|
||
|
|
created.
|
||
|
|
|
||
|
|
@param cls: Same as self.
|
||
|
|
"""
|
||
|
|
if len(cls.__abstractmethods__):
|
||
|
|
raise NotImplementedError('Can\'t instantiate class `' + \
|
||
|
|
cls.__name__ + '\';\n' + \
|
||
|
|
'Abstract methods: ' + \
|
||
|
|
", ".join(cls.__abstractmethods__))
|
||
|
|
|
||
|
|
return object.__new__(self)
|