Class factory to produce simple struct-like classes?

Question

While investigating Ruby I came across this to create a simple Struct-like class:

Person = Struct.new(:forname, :surname)
person1 = Person.new(\'John\', \'Do         


        

Answer 1

This is following up on Cide's answer (and probably only interesting for people who want to dig deeper).

I experienced a problem using Cide's updated definition of Struct(), the one using __slots__. The problem is that instances of returned classes have read-only attributes:

>>> MS = Struct('forename','lastname')
>>> m=MS()
>>> m.forename='Jack'
Traceback (most recent call last):
  File "", line 1, in 
AttributeError: 'MyStruct' object attribute 'forename' is read-only

Seems that __slots__ is blocking instance-level attributes when there are class attributes of same names. I've tried to overcome this by providing an __init__ method, so instance attributes can be set at object creation time:

def Struct1(*args, **kwargs):
    def init(self):
        for k,v in kwargs.items():
            setattr(self, k, v)
    name = kwargs.pop("name", "MyStruct")
    kwargs.update(dict((k, None) for k in args))
    return type(name, (object,), {'__init__': init, '__slots__': kwargs.keys()})

As a net effect the constructed class only sees the __init__ method and the __slots__ member, which is working as desired:

>>> MS1 = Struct1('forename','lastname')
>>> m=MS1()
>>> m.forename='Jack'
>>> m.forename
'Jack'