Question

write a program that keeps names and email addresses in a dictionary as key-value pairs. the program should display a menu that lets the user look up a person’s email address, add a new name and email address, change an existing email address, and delete an existing name and email address. the program should save the data stored in a dictionary to a file when the user exits the program. each time the program starts, it should retrieve the data from the file and store it in a dictionary. the program should include the following functions: a. a function to display a menu. b. a function to look up a person’s email address. c. a function to add a new name and email address. d. a function to change an email address. e. a function to delete a name and email address. f. a function to load emails from a file. g. a function to save emails in a file. h. write main function with a loop that displays the menu allowing the user to select an operation from the menu; the program continue until the user enter 5. i. validate all user input. your program should check user input; for example, if the user wants to search or delete a name that does not exist in the dictionary, you should print something like the name is not in the database. if the user selects invalid operation from the menu, the program prints an error and allows the user to renter a valid operation; the program continue asking for a valid operation until a user selects a valid operation.

Answer 1

To write a program that keeps names and email addresses in a dictionary as key-value pairs check the code given below.

What is key-value pairs?

In a key-value pair, two related data elements are combined: a value, which is a variable that belongs to the set (for example, male/female, green, 100), and a key, which is a constant that defines the data set (for example, gender, color, price).

A key-value pair could look something like this when fully formed:

gender = male

color = green

price > 100

↓↓↓//Python code//↓↓↓

import pickle

import sys

try:

   f=open('email.dat','rb')

   d=pickle.load(f)  

   f.close()

     

except:    

   d={}

while True:

   print('\n1. Find a email address')

   print('2. Add name and email address')

   print('3. Change an email address')

   print('4. Delete an email address')

   print('5. Exit\n')

   choice=input('\nEnter a choice: ')

   if choice:

       choice=int(choice)

   else:

       print('\nEnter a number')

       continue    

   if choice == 1:

       while True:

           name=input('\nEnter the name ')

           if name:

               if name in d:

                   print('\n%s is the email id of %s \n' % (d[name],name))

                   break

               else:

                   print('\n Email not found \n')

                   break

           else:

               print('\nName cannot be empty\n')

               continue

           

   elif choice==2:

       while True:            

       

           name=input('\nEnter the name ')

           if name:

               break;

           else:

               print('\nName cannot be empty \n')

               continue

       while True:            

       

           email=input('\nEnter the email address ')

           if email:

               d[name]=email

               break

           else:

               print('\nEmail cannot be empty\n')

               continue

           

   elif choice==3:

       while True:            

       

           name=input('\nEnter the name to change the email address ')

           if name:

               if name in d:

                   email=input('\nEnter the new email address ')

                   d[name]=email

                   print('\nEmail address changed \n')

                   break;

               else:

                   print('\nName not found \n')

                   break

           else:

               print('\nName cannot be empty \n')

               continue

           

   elif choice == 4:

       while True:            

       

           name=input('\nEnter the name to remove ')

           if name:

               if name in d:

                   del d[name]

                   print('\nName and Email address removed \n ')

                   break;

               else:

                   print('\nName not found \n')

                   break

           else:

               print('\nName cannot be empty\n')

               continue

   elif choice == 5:

       

       f=open('email.dat','wb')

       pickle.dump(d,f)

       f.close()

       sys.exit()

   else:

       print('\nEnter a valid choice ')    

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