What do these lines print?class Base(): """ My base class """ __nb_instances = 0 def __init__(self): Base.__nb_instances += 1 self.id = Base.__nb_instancesclass User(Base): """ My User class """ passu = User()print(u.id)
Question
What do these lines print?class Base(): """ My base class """ __nb_instances = 0 def init(self): Base.__nb_instances += 1 self.id = Base.__nb_instancesclass User(Base): """ My User class """ passu = User()print(u.id)
Solution
The code defines two classes: Base and User. User is a subclass of Base.
In the Base class, a class variable __nb_instances is defined and initialized to 0. This variable is intended to keep track of the number of instances of the Base class (and its subclasses) that have been created.
In the __init__ method of the Base class, __nb_instances is incremented by 1 each time an instance is created. The instance variable id is then set to the current value of __nb_instances.
The User class doesn't define any additional behavior, so it inherits all the behavior of the Base class.
When u = User() is executed, a new instance of User is created. Because User is a subclass of Base, this triggers the __init__ method of the Base class, which increments __nb_instances and sets u.id to the new value of __nb_instances.
Finally, print(u.id) prints the id of the u object, which is 1. So, the output of this code is 1.
Similar Questions
What do these lines print?class Base(): """ My base class """ __nb_instances = 0 def __init__(self): Base.__nb_instances += 1 self.id = Base.__nb_instancesfor i in range(3): b = Base()print(b.id)
class Base(): """ My base class """ __nb_instances = 0 def __init__(self): Base.__nb_instances += 1 self.id = Base.__nb_instancesclass User(Base): """ My User class """ def __init__(self): super().__init__() self.id = 89u = User()print(u.id)
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What do these lines print?class User: id = 1u = User()print(u.id)
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