get a dictionary of an attribute in all instances

Question

class Players:
def __init__(self, username, score):
    self.username = username
    self.score = score

If I create a class and some instances of it with different scores, how can I get a dictionary with the username as key and the score as value for all instances? I will change the score after creating the instance, so appending score and username to the dictionary when creating the instance can not work.

thank you so much

Answer 1

A tricky way is to use attrgetter from operator

from operator import attrgetter

p1 = Players('p1', 10)
p2 = Players('p2', 11)
p3 = Players('p3', 12)

instances = [p1, p2, p3]

d = dict(map(attrgetter('username', 'score'), instances))
print(d)
# {'p1': 10, 'p2': 11, 'p3': 12}

or without any extra imports

d = dict((obj.username, obj.score) for obj in instances)

Answer 2

As an easiest way, you can do

player_instance = Player("name", 0)
...
player_instance.__dict__

This dictionary is also linked to the object, so changes to the dictionary will change the instance

player_instance.__dict__["score"] = 123456789
# player_instance.score is now 123456789

Though, you don't necessarily want to have your object accept changes though this dictionary. Generally what you would usually do is make a method that generates your desired data structure for you

class Players:
    def __init__(self, username, score):
        self.username = username
        self.score = score
    @property
    def as_dict(self):
        return {"username": self.username, "score": self.score}