python代码中的无限循环错误

Question

I am learning how to code through this book called "Headfirst Programming", which I am really enjoying so far.

One of the projects in the book uses the following code:

def save_transaction(price, credit_card, description):
file = open("transactions.txt", "a")
file.write("%s%07d%s\n" % (credit_card, price * 100, description))
file.close()


items = ['Donut','Latte','Filter','Muffin']
prices = [1.50,2.0,1.80,1.20]` 
running = true

while running:
      option = 1
      for choice in items:
         print(str(option) + ". " + choice)
         option = option + 1
print(str(option) + ". Quit"))
choice = int(input("choose an option: "))
if choice == option:
   running = false
else: 
   credit_card = input("Credit card number: ")
   save_transaction(prices[choice - 1], credit_card, items[choice - 1])

I can see the logic behind using the "if choice == option then running = false" code (it lets the user add an arbitrary number of items), but this code, as is, runs an infinite loop in the shell. This is strange because I copied it directly from the book and the author is using python 3.0, as am I.

Does anyone have a guess as to why this code runs an infinite loop and how to solve this problem, while keeping the code's core functionality intact?

Thanks

Answer 1

As you've probably read, Python uses indentation to identify blocks of code.

So...

while running:
      option = 1
      for choice in items:
         print(str(option) + ". " + choice)
         option = option + 1

will run forever, and

print(str(option) + ". Quit"))
choice = int(input("choose an option: "))
if choice == option:
   running = false
else: 
   credit_card = input("Credit card number: ")
   save_transaction(prices[choice - 1], credit_card, items[choice - 1])

is never reached. Simply fix the indentation and you should be right.

Answer 2

It's pretty clear that the indentation here is wrong -- since the whole body of the function should be indented relative to the def save_transaction(price, credit_card, description): line.

Hence, I suspect that there's also a problem with the indentation below the while running line, and that the lines which change the value of running should be inside the loop.

Answer 3

You need to indent forward all the lines starting from print(str(option) + ". Quit")) . Align them at the same level as for choice in items: .