File operation - 52 days - Learn Python online for 100 days.

I remember it very clearly, I have posted this content, but I don't know why it disappeared.

Record#

Catbox

Today I learned backtracking, try-except.
try and except are a pair and need to appear together.
Basic logic: try code, except code when there is an error.
Use except Exception as err: print(err) to print error messages.
Set debug mode on the first line, debugMode = False.
1. if debugMode: print(traceback)
2. This makes it convenient to control whether to display system error messages.
Today's exercise is to write an order list for a pizza shop, which involves the following points:
1. Use the name as the dictionary key for order information, and other information as the dictionary value. Write it to a local file in this format after converting to a string.
2. Because it is writing a dictionary, it needs to be read first, assigned to the dictionary, then write new data, and finally save it.
3. Use eval() when reading.
4. Use a for loop to view, first key, value in item(), which is an operation on the dictionary. Since the value is an array, simply use for name, print name.
5. The correct answer does not use a dictionary, but uses a two-dimensional array, which is relatively simpler. Just use array.append.

CODE#

import os, time
debugMode = False
print("🌟Dave's Dodgy Pizzas🌟")
again="y"
def addpiz():
  uname = input("Name please > ")
  try:
    piznum = int(input("How many pizzas? > "))
  except:
    piznum = int(input("You must input a numerical character, try again. > "))
	
  pizsize = input("What size? s/m/l > ").lower()
  
  if pizsize == "s":
    pizcost = 1.99
  elif pizsize == "m":
    pizcost = 9.99
  elif pizsize == "l":
    pizcost = 19.99

  toping  = input("toping please > ")
  total = pizcost*piznum
  print(f"Thanks {uname}, your pizzas will cost {total}")
  try:
    f = open("piz.list","r")
    pizlist  = eval(f.read())
    f.close()
  except:
    pizlist={}
  pizlist[uname]=[toping,pizsize,piznum,total]
  f = open("piz.list","w")
  f.write(str(pizlist))
  f.close

def viewpiz():
  try:
    f = open("piz.list","r")
    pizlist  = eval(f.read())
    f.close()
  except:
    print("The piz list is empty.")
    time.sleep(2)

  print(f"{'Name': ^10}{'Topping': ^10}{'Size': ^10}{'Quantity': ^10}{'Total': ^10}")
  for key,value in pizlist.items():
    print(f"{key: ^10}",end="")
    for name in value:
      print(f"{name: ^10}",end="")
    print()

    


try:
  f = open("piz.list","r")
  pizlist  = eval(f.read())
  f.close()
except:
  print("The piz list is empty.")
  time.sleep(2)
  os.system("clear")

while True:
  if again == "y":
    menu = int(input("1. Add\n2. View\n"))
    if menu == 1:
      addpiz()
    elif menu == 2:
      viewpiz()
  again = input("again? y/n")

Translation: