Question

Define the instance method inc_num_kids() for PersonInfo. inc_num_kids increments the member data num_kids. Sample output for the given program with one call to inc_num_kids():

Answer 1

Answer:

This is the instance method inc_num_kids()

def inc_num_kids(self):

       self.num_kids += 1

Explanation:

The first line is the definition of function inc_num_kids() which has a parameter self. self is basically an instance of  class PersonInfo

self.num_kids += 1 this statement incremented the data member num_kids by 1. This means that the instance method inc_num_kids, using instance self, increments the value of num_kids data member by 1.

The complete program is as following:

class PersonInfo:  #class name PersonInfo

   def __init__(self):   #constructor of the class

       self.num_kids = 0  # data member num_kids

   def inc_num_kids(self):  # method inc_num_kids

       self.num_kids += 1  #increments num_kids by 1

person1 = PersonInfo()  #creates object person of class PersonInfo

print('Kids:', person1.num_kids)  # prints num_kids value before increment

person1.inc_num_kids()  #calls inc_num_kids method to increment num_kids

print('New baby, kids now:', person1.num_kids) #prints the value of num_kids after increment by inc_num_kids method

The person1 object first access the initial value of num_kids initialized by the constructor. So the first value of num_kids is 0. self.num_kids = 0  This statement assigns the value 0 to num_kids data member. Next the method inc_num_kids() using the object person1. Now when this method is called the value of data member num_kids is incremented to 1.

So previously the value was 0 which now increments by 1 and becomes 1. Last print statement displays this new value which is incremented by the inc_num_kids() method.

Hence the output is:

Kids: 0

New baby, kids now: 1

The program along with its output is attached.