Question

我对我的代码略有不满。我对python的了解非常有限，但我试图退出循环来显示某人选择的项目。我试过if语句不起作用。考虑一个def语句，但不太确定如何实现它和Return是一个想法，但显然需要def语句才能工作。

非常感谢任何帮助。

P.S我不知道如何上传CSV文件，但以下链接是我的目标：https://dl.dropboxusercontent.com/u/31895483/teaching%20delivered/FE/2013-14/Access%20-%20Prg/assignment/menu2.swf

import csv

f = open("menu.csv", "r")       #Has items for the menu and is read only

spent = 0

order = []

menu = []

for line in f:

        line = line.rstrip("\n")

        dish = line.split(',')

        menu = menu + [dish]
f.close()

                       #Menu imported into python, no need to leave file open
while True:

    dishes = -1

    for dish in menu:

        if dishes == -1:
                print ("Dish No".ljust(10), end="")
        else:
                print(str(dishes).ljust(10), end="")
        print(dish[0].ljust(15), end="")
        print(dish[1].ljust(30), end="")
        print(dish[2].ljust(15), end="")
        print(dish[3], end="\n\n")
        dishes += 1
    reply = input("Please choose your first item: ")
    print()
    spent = spent + float(menu[int(reply)+1][2])
    order = order + [reply]
    print(len(order), "choices made so far =", order, "and cost = £ ", spent)
    print()
    print ("Please choose an item from the menu (0-9 or press Q to end): ")
    print()

Answer 1

您需要做的就是检查退出条件，然后使用break statement来摆脱循环。

while True:
    # other stuff here

    reply = input("Please choose a menu item:")
    if reply.upper() == 'Q':
        break # Break out of the while loop.

    # We didn't break, so now we can try to parse the input to an integer.
    spent = spent + float(menu[int(reply)+1][2])

这种while True + other_code + if condition: break模式很常见，至少有两个好处：

你正在使用公认的习语，所以当你在其他地方遇到它们时，你会认出它们。
其他人（包括您未来的自己）在阅读时能够理解您的代码。

Answer 2

我喜欢的一个很酷的技巧

my_menu_choices = iter(lambda : input("Please choose a menu item:").lower(),"q")
for i,dish in dishes:
   print("%d. %s"%(i,dish))
print("Q. type q to QUIT")
my_menu_choices = list(my_menu_choices)
print("You Choose: %s"%my_menu_choices)

如何退出循环以显示所选列表项

2 个答案: