Test Series - python

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Test Number 110/108

Q: Methods of a class that provide access to private members of the class are called as ______ and ______
A. getters/setters
B. __repr__/__str__
C. user-defined functions/in-built functions
D. __init__/__del__
Solution: The purpose of getters and setters is to get(return) and set(assign) private instance variables of a class.
Q: Which of these is a private data field?

def Demo:
def __init__(self):
    __a = 1
    self.__b = 1
    self.__c__ = 1
    __d__= 1
A. __a
B. __b
C. __c__
D. __d__
Solution: Variables such as self.__b are private members of the class.
Q: What will be the output of the following Python code?

class Demo:
     def __init__(self):
         self.a = 1
         self.__b = 1
 
     def get(self):
         return self.__b
 
obj = Demo()
print(obj.get())
A. The program has an error because there isn’t any function to return self.a
B. The program has an error because b is private and display(self) is returning a private member
C. The program has an error because b is private and hence can’t be printed
D. The program runs fine and 1 is printed
Solution: Here, get(self) is a member of the class. Hence, it can even return a private member of the class. Because of this reason, the program runs fine and 1 is printed.
Q: What will be the output of the following Python code?

class Demo:
     def __init__(self):
         self.a = 1
         self.__b = 1
     def get(self):
         return self.__b
obj = Demo()
obj.a=45
print(obj.a)
A. The program runs properly and prints 45
B. The program has an error because the value of members of a class can’t be changed from outside the class
C. The program runs properly and prints 1
D. The program has an error because the value of members outside a class can only be changed as self.a=45
Solution: It is possible to change the values of public class members using the object of the class.
Q: Private members of a class cannot be accessed.
A. True
B. False
C. ..
D. ..
Solution: Private members of a class are accessible if written as follows: obj._Classname__privatemember. Such renaming of identifiers is called as name mangling.
Q: The purpose of name mangling is to avoid unintentional access of private class members.
A. True
B. False
C. ..
D. ..
Solution: Name mangling prevents unintentional access of private members of a class, while still allowing access when needed. Unless the variable is accessed with its mangled name, it will not be found.
Q: What will be the output of the following Python code?

class fruits:
    def __init__(self):
        self.price = 100
        self.__bags = 5
    def display(self):
        print(self.__bags)
obj=fruits()
obj.display()
A. The program has an error because display() is trying to print a private class member
B. The program runs fine but nothing is printed
C. The program runs fine and 5 is printed
D. The program has an error because display() can’t be accessed
Solution: Private class members can be printed by methods which are members of the class.
Q: What will be the output of the following Python code?

 class student:
    def __init__(self):
        self.marks = 97
        self.__cgpa = 8.7
    def display(self):
        print(self.marks)
obj=student()
print(obj._student__cgpa)
A. The program runs fine and 8.7 is printed
B. Error because private class members can’t be accessed
C. Error because the proper syntax for name mangling hasn’t been implemented
D. The program runs fine but nothing is printed
Solution: Name mangling has been properly implemented in the code given above and hence the program runs properly.
Q: Which of the following is false about protected class members?
A. They begin with one underscore
B. They can be accessed by subclasses
C. They can be accessed by name mangling method
D. They can be accessed within a class
Solution: Protected class members can’t be accessed by name mangling.
Q: What will be the output of the following Python code?

class objects:
    def __init__(self):
        self.colour = None
        self._shape = "Circle" 
 
    def display(self, s):
        self._shape = s
obj=objects()
print(obj._objects_shape)
A. The program runs fine because name mangling has been properly implemented
B. Error because the member shape is a protected member
C. Error because the proper syntax for name mangling hasn’t been implemented
D. Error because the member shape is a private member
Solution: Protected members begin with one underscore and they can only be accessed within a class or by subclasses.

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