Python to achieve shopping process ideas and code

Requirements:

After launching the program, let the user enter a salary and print out a list of items with serial Numbers
The user enters the serial number of the product to purchase the corresponding product, or enters' q 'to exit the purchase interface
After selecting the goods, check whether the balance is enough, if enough, direct deduction, insufficient prompt insufficient balance
After each purchase, or enter 'q' to exit the purchase interface, the user will be prompted: Do you want to continue the purchase? (Y/N) to achieve multiple purchases
If the user purchases the goods, print out the list of purchased goods, total amount and balance; If the user does not buy any goods, print: transaction closed, shopping failed
Readme:

Run the program, enter your salary, and select the item you want to buy based on the serial number of the item list. You can choose multiple purchases or no purchases

Flow chart:

Code:

#  Simple shopping applet 

product_list = [
  ['surface pro 4', 7800],
  ['dell xps 15', 12000],
  ['macbook', 12000],
  [' millet 6', 2499],
  ['iphone7', 4600],
  [' nuts Pro', 1499]
]
shopping_list = []


#  Determine if the salary format entered is correct 
while True:
  salary = input('\n Please enter your salary: ')
  if not salary.isdigit():          #  Salary is not a number. Close the loop 
    print('\n Incorrect input format! Please re-enter ...')
    continue
  break


balance = salary = int(salary)

print('\n----------- Welcome to buy ------------\n')

#  Generates a list of items with serial Numbers 
for index, item in enumerate(product_list):
  print(index, item)


#  Determine if the input serial number meets the requirements 
while True:

  while True:
    i = input('\n Enter the item number you want to buy, or enter  q  Cancel the purchase: ')
    if i == 'q':                 #  The input  q  Exit the purchase interface 
      while True:
        a = input('\n Do you want to keep buying? (Y/N) : ')
        if a != 'n' and a != 'N' and a != 'y' and a != 'Y':
          print('\n Incorrect input format. Please try again ...')
          continue
        elif a == 'y' or a == 'Y':         #  Continue to buy 
          break
        else:                    #  After buying 
          if balance == salary:       #  I didn't buy anything 
            print('\n The transaction ends and the purchase fails ...')
            exit()
          else:               #  settlement   
            print('\n You have successfully purchased the following products: \n')
            for item in shopping_list:
              print(item)
            print('\n Total amount of consumption  %d  Yuan, balance  %d  yuan ' % (salary - balance, balance))
            exit()
      continue

    if not i.isdigit():             #  The serial number is not a number. End the loop 
      print('\n Incorrect input format! Please re-enter ...')
      continue

    i = int(i)

    if i < 0 or i >= len(product_list):  #  Incorrect serial number range, end loop 
      print('\n This item does not exist, please re-enter ...')
      continue
    break

  product = product_list[i]
  price = int(product[1])

  #  Judge whether the balance is sufficient, enough direct deduction, not enough to remind 
  if price <= balance:
    balance -= price
    shopping_list.append(product_list[i])
    print('\n You have made a successful purchase  %s  , the current balance is  %d  yuan ' %(product, balance))
  else:
    print('\n Purchase failed, your balance is insufficient ...')

  while True:
    a = input('\n Do you want to keep buying? (Y/N) : ')
    if a != 'n' and a != 'N' and a != 'y' and a != 'Y':
      print('\n Incorrect input format. Please try again ...')
      continue
    break

  if a == 'Y' or a == 'y':
    continue
  else:
    break

if balance == salary:
  print('\n The transaction ends and the purchase fails ...')
  exit()
else:
  print('\n You have successfully purchased the following products: \n')
  for item in shopping_list:
    print(item)
  print('\n Total amount of consumption  %d  Yuan, balance  %d  yuan ' %(salary-balance, balance))
  exit()