Question 4

Correct answers: C, D

class Lower:
    def __init__(self):
        self.color = "blue"
 
 
print(Lower().color)  # blue
 
 
class Working:
    def __init__(self):
        raise KeyError
 
 
working = Working()  # KeyError
 
 
class Middle:
    def __init__():
        self.color = None
 
 
# middle = Middle()
# TypeError: __init__() takes 0 positional
# arguments but 1 was given
 
 
class Upper:
    def __init__(self):
        return False
 
 
# upper = Upper()
# TypeError: __init__() should return None, not 'bool'

A.

This choice does not contain a usable constructor because it defines the __init__ method with a return statement that returns a boolean value. Constructors in Python should initialize the object's state, not return values. This implementation does not follow the standard constructor format.

B.

This choice does not contain a usable constructor because the __init__ method is missing the self parameter. In Python, the self parameter is necessary to reference the instance of the class, so this constructor would not work as intended.

C.

This choice also contains a usable constructor, despite raising a KeyError exception within it. The presence of the __init__ method with the self parameter makes it a valid constructor. While raising an exception may not be common practice, it still fulfills the requirement of initializing the object.

D.

This choice contains a usable constructor because it defines the __init__ method with the self parameter, which is the standard way to define a constructor in Python classes. It initializes an instance variable color with the value "blue".