Kent Johnson wrote:
> Try this:
>
> def fromFile(path):
> adict = {}
> alist = []
> #...
> #some part to read a file and to process data
> return MyClass(parameter1,parameter2,...,d)
> fromFile = staticmethod(fromFile)
>
> then client code will look like this:
> aClass = MyClass.fromFile('a/file/path')
A few more notes:
- There is no need to make fromFile a staticmethod of MyClass, it could also be
a module level
function. Writing it as a staticmethod puts it in the namespace of MyClass
which may be handy.
- If you intend to subclass MyClass, the subclass constructors have compatible
signatures and you
want to be able to create subclasses with the same factory, a classmethod might
work better.
>>> class A(object):
... def __init__(self, val):
... self.val = val
... def show(self):
... print 'A.val:', self.val
... def factory(cls, val):
... return cls(val)
... factory = classmethod(factory)
...
>>> a=A.factory(3) # calls A.factory(A, 3)
>>> a.show()
A.val: 3
>>>
>>> class B(A):
... def show(self):
... print 'B.val:', self.val
...
>>> b=B.factory(22) # calls A.factory(B, 22)
>>> b.show()
B.val: 22
- Finally, if you are using Python 2.4, you may prefer the decorator syntax for
defining
classmethods and staticmethods:
class A(object):
...
@classmethod
def factory(cls, val):
return cls(val)
Kent
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