Q.Write a program to input your friend’s, names and their phone numbers and store them in the dictionary as the key-value pair. Perform the following operations on the dictionary:

A dictionary {name: phone} handles every operation with one built-in each.

for n, p in phonebook.items(): print(n, p)   # a) display all
phonebook['Kabir'] = '9844444444'            # b) add new pair
del phonebook['Aman']                        # c) delete a friend
phonebook['Zoya'] = '9855555555'             # d) modify a number
print('Riya' in phonebook)                   # e) membership check -> True …

Build the dictionary

# Friends' phone book
phonebook = {}
n = int(input("How many friends? "))
for i in range(n):
    name  = input("Name  : ")
    phone = input("Phone : ")
    phonebook[name] = phone         # name is the key, number the value

Sample data used below:

phonebook = {'Riya': '9811111111', 'Aman': '9822222222', 'Zoya': '9833333333'}

a) Display the name and phone number of all friends

for name, phone in phonebook.items():
    print(name, ":", phone)

Riya : 9811111111
Aman : 9822222222
Zoya : 9833333333

b) Add a new key-value pair and display the modified dictionary

Assigning to a key that does not exist creates a new pair.

phonebook['Kabir'] = '9844444444'
print(phonebook)

{'Riya': '9811111111', 'Aman': '9822222222', 'Zoya': '9833333333', 'Kabir': '9844444444'}

c) Delete a particular friend

name = input("Friend to delete: ")        # e.g. Aman
if name in phonebook:
    del phonebook[name]
    print(phonebook)
else:
    print(name, "not found")

{'Riya': '9811111111', 'Zoya': '9833333333', 'Kabir': '9844444444'}

d) Modify the phone number of an existing friend

Assigning to a key that already exists overwrites its value — same syntax as (b), opposite effect.

name = input("Friend to modify: ")        # e.g. Zoya
if name in phonebook:
    phonebook[name] = input("New phone: ")   # e.g. 9855555555
    print(phonebook)

{'Riya': '9811111111', 'Zoya': '9855555555', 'Kabir': '9844444444'}

e) Check whether a friend is present

name = input("Friend to search: ")        # e.g. Riya
if name in phonebook:
    print(name, "is present")
else:
    print(name, "is not present")

Riya is present
``` …