construct instance variables from dictionnay

Question

I have written a class, in which the constructor receives a dictionary, as shown in the following code:

class Test:
     def __init__(self, **kwargs):
           for key, value in kwargs.items():
               self.key = value

what i want to do at the end is the ability to reference each key as shown in the following piece of code:

T = Test(age=34, name='david')
print(T.age)

instead i get keyword can't be an expression..

this subject could benefit from a performance discussion, which method is more effecient. — rachid el kedmiri, Sep 14 '17 at 10:19

score 5 · Accepted Answer · edited Sep 14 '17 at 09:51

5

You can update the class dict:

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

You can also query vars and update (one should prefer this to invoking __dunder__ attributes directly).

class Test:
     def __init__(self, **kwargs):
           vars(self).update(kwargs)

edited Sep 14 '17 at 09:51

cs95

answered Sep 14 '17 at 09:38

Netwave

2

this is cleaner than using `setattr`. +1 – Phydeaux Sep 14 '17 at 09:39
Related: https://stackoverflow.com/questions/739625/setattr-with-kwargs-pythonic-or-not – Pierre Geier Sep 14 '17 at 09:47

score 1 · Answer 2 · answered Sep 14 '17 at 09:38

1

You are setting only the attribute T.key. If you want to dynamically set attributes based on the name of the key, you need setattr:

for key, value in kwargs.items():
    setattr(self, key, value)

answered Sep 14 '17 at 09:38

Phydeaux

Magic method `__getattr__` works too. def __init__(self, **kwargs): self.keywords = kwargs def __getattr__(self, key): return self.keywords[key] – Pierre Geier Sep 14 '17 at 09:38
@PierreGeier Avoid using dunder methods. – cs95 Sep 14 '17 at 09:41

2 Answers2