More __init__ methods

[Duncan Booth]

Mr.SpOOn <mr.spoon21 at gmail.com> wrote:

> Now I must pass a and b to the main constructor and calculate them in
> the classmethods.
> 
> class foo:
>     def __init__(self, a, b):
>          self.a = a
>          self.b = b
> 
>     @classmethod
>     def from_string(self, ..):
>           ...
>           ...
> 
> What I mean is: I can't use anymore __init__ as the default
> constructor, but I always have to specify the way I'm creating my
> object. Am I right? I'm asking just to be sure I have understood.

There is a really big advantage to being explicit in this situation: you no 
longer have to make sure that all your constructors use a unique set of 
types. Consider:

class Location(object):
    def __init__(self, lat, long): ...

    @classmethod
    def from_city(name): ...

    @classmethod
    def from_postcode(name): ...

'from_string' is a bad name here for your factory method: you should try to 
make it clear what sort of string is expected.

-- 
Duncan Booth http://kupuguy.blogspot.com