如何解决Python：子类type来创建专门的类型例如“ int列表”
|| 我试图对ѭ0进行子类化，以创建允许构建专门类型的类。例如ListType
>>> ListOfInt = ListType(list,value_type=int)
>>> issubclass(ListOfInt,list)
True
>>> issubclass(list,ListOfInt)
False
>>> # And so on ...
type
list of int
XML string
class SpzType(type):
__metaclass__ = abc.ABCMeta
@classmethod
def __subclasshook__(cls,C):
return NotImplemented
def __new__(cls,base,**features):
name = \'SpzOf%s\' % base.__name__
bases = (base,)
attrs = {}
return super(SpzType,cls).__new__(cls,name,bases,attrs)
def __init__(self,**features):
for name,value in features.items():
setattr(self,value)
>>> class SimpleType(SpzType): pass
>>> t = SimpleType(int)
>>> issubclass(t,int)
True
>>> issubclass(int,t)
False
t
SpzType
>>> isinstance(t,SpzType)
TypeError: __subclasscheck__() takes exactly one argument (0 given)
pdb.pm()
>>> SpzType.__subclasscheck__(SimpleType)
TypeError: __subclasscheck__() takes exactly one argument (0 given)
abc
解决方法
我不太确定您要实现什么目标。也许最好使用
collections
abc
def listOf(base,types={},**features):
key = (base,) + tuple(features.items())
if key in types:
return types[key]
else:
if not isinstance(base,type):
raise TypeError(\"require element type,got \'%s\'\" % base)
class C(list):
def __init__(self,iterable=[]):
for item in iterable:
try: # try to convert to desired type
self.append(self._base(item))
except ValueError:
raise TypeError(\"value \'%s\' not convertible to %s\"
% (item,self._base.__name__))
# similar methods to type-check other list mutations
C.__name__ = \"listOf(%s)\" % base.__name__
C._base = base
C.__dict__.update(features)
types[key] = C
return C
listOf(int) is listOf(int)
True
class SpzType(abc.ABCMeta):
def __subclasshook__(self,C):
return NotImplemented
def __new__(cls,base,**features):
name = \'SpzOf%s\' % base.__name__
bases = (base,)
attrs = {}
new_spz = super(SpzType,cls).__new__(cls,name,bases,attrs)
new_spz.__subclasshook__ = classmethod(cls.__subclasshook__)
return new_spz
def __init__(self,**features):
for name,value in features.items():
setattr(self,value)
abc.ABCMeta
__subclasshook__
__subclasshook__
ABCMeta
__init__()
__classinit__()
def template_class(cls,classcache={}):
def factory(element_type=None,**features):
key = (cls,element_type) + tuple(features.items())
if key in classcache:
return classcache[key]
newname = cls.__name__
if element_type or features:
newname += \"(\"
if element_type:
newname += element_type.__name__
if features:
newname += \",\"
newname += \",\".join(key + \"=\" + repr(value)
for key,value in features.items())
newname += \")\"
newclass = type(cls)(newname,(cls,),{})
if hasattr(newclass,\"__classinit__\"):
classinit = getattr(cls.__classinit__,\"im_func\",cls.__classinit__)
newclass = classinit(newclass,element_type,features) or newclass
else:
if element_type:
newclass.element_type = element_type
for key,value in features.items():
setattr(newclass,key,value)
classcache[key] = newclass
return newclass
factory.__name__ = cls.__name__
return factory
@template_class
class ListOf(list):
def __classinit__(cls,features):
if isinstance(element_type,type):
cls.element_type = element_type
else:
raise TypeError(\"need element type\")
def __init__(self,iterable):
for item in iterable:
try:
self.append(self.element_type(item))
except ValueError:
raise TypeError(\"value \'%s\' not convertible to %s\"
% (item,self.element_type.__name__))
# etc.,to provide type conversion for items added to list
Floatlist = ListOf(float)
Intlist = ListOf(int)
print FloatList((1,2,3)) # 1.0,2.0,3.0
print IntList((1.0,2.5,3.14)) # 1,3
print ListOf(float)((1,3))
print ListOf(int)((1.0,3.14))
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