Passing new fields to an object

[Peter Otten]

Paulo da Silva wrote:

> On 12-06-2015 17:17, Peter Otten wrote:
>> Paulo da Silva wrote:
>> 
> ...
> 
>> 
>>>>> import types
>>>>> class C(types.SimpleNamespace):
>> ...     pass
>> ...
>>>>> c = C(f1=1, f2=None)
>>>>> c
>> C(f1=1, f2=None)
>> 
> 
> Thanks for all your explanations.
> This solution works. Would you please detail a little on how it works?
> Or just point me out some readings.
> I am confused because types.SimpleNamespace seems to be a class!

It *is* a class, and by making C a subclass of SimpleNamespace C inherits 
the initialiser which does the actual work of updating the __dict__ of the C 
instance.

> From docs ...:

> class SimpleNamespace:
>     def __init__(self, **kwargs):
>         self.__dict__.update(kwargs)

The actual implementation is written in C (the language used to implement 
the CPython interpreter), but following the example in the docs you can make 
your own SimpleNamespace...

>>> class MySimpleNamespace:
...     def __init__(self, **parms): self.__dict__.update(parms)
... 
>>> m = MySimpleNamespace(a=1, b=2)
>>> m.a
1
>>> m.b
2

and when you subclass it the subclass inherits the behaviour:

>>> class C(MySimpleNamespace):
...     pass
... 
>>> c = C(x=10, y=20)
>>> c.x
10
>>> c.y
20