Functional requirements:

• Query the contact person, input the name, you can query the contact information in the current address book, if the contact person exists, output the contact information, if not, inform
• Insert a contact, and you can create a new contact in the address book. If the contact already exists, ask if you want to modify the contact information. If not, create a new contact
• Delete contact, you can delete contact, if the contact does not exist, inform
• Enter the command to exit the address book

Specific code implementation:

 1 #!/usr/bin/env python3
 2 # -*- coding: utf-8 -*-
 3 # @Time    : 2018/3/26 10:01
 4 # @Author  : yang
 5 # @File    : Exercise.py
 6 # @Software: PyCharm
 7 
 8 #Mail list
 9 print('''|---Welcome to the address book---|
10 |---1,Query contact info ---|
11 |---2,Insert new contact---|
12 |---3,Delete contact information---|
13 |---4,Exit address book program---|
14 ''')
15 addressBook = {'Xiao Yang':12345678,'Xiao Zhang':12345679,'Xiao Zhao':12345670}
16 while 1:
17     order_code = input('Please enter the instruction code:')
18     if order_code.isdigit() == False:    #Judge whether the instruction is only composed of numbers
19         print('The format of the instruction code you entered is wrong, please input again according to the prompt!')
20         continue
21     item = int(order_code)    #Convert input instruction to integer
22 
23     if item == 4:
24         print('Thank you for using the address book!')
25         break      #End cycle
26     #Enter contact name
27     name = input('Please enter contact name:')
28     if item == 1:      #Query contact info 
29         if name in addressBook:
30             print(name,':',addressBook[name])
31             continue     #End current cycle
32         else:
33             print('The contact does not exist.')
34     if item == 2:     #New contact
35         if name in addressBook:
36             print('The contact you entered already exists in the address book--->>',name,':',addressBook[name])
37             is_Edit = input('Need to modify contact information(Y/N)')    #Determine whether the current contact information needs to be modified
38             if is_Edit == 'Y':
39                 userphone = input('Please enter the contact number:')
40                 addressBook[name] = userphone
41                 print(addressBook)
42                 continue
43             else:
44                 continue
45         else:
46             userphone = input('Please enter the contact number:')
47             addressBook[name]=userphone
48             print('Contact added successfully!')
49             print(addressBook)
50             continue
51     if item == 3:    #Delete Contact 
52         if name in addressBook:
53             del addressBook[name]
54             print('Contact deleted successfully!')
55             print(addressBook)
56             continue
57         else:
58             print('Contact does not exist')