Question

我主要使用的是Python 3.2，但仅仅是出于可视化目的而转向2.7。我似乎无法使循环形成无限循环，例如，如果用户输入错误的短语，则在输入错误的变量后代码就会中断。

 measure = raw_input("what form of measurement do you want to use: 
 (enter CM or IN): ")
 while True:
     if measure == str('cm'):
         break
     elif measure == str("in"):
         break
     else:
         measure =  input("please enter cm or in")
         continue

Answer 1

当我尝试它时，您尝试在raw_input块中使用else上的输入时抛出错误。试试以下内容：

measure = raw_input("what form of measurement do you want to use: 
 (enter CM or IN): ")
 while True:
     if measure == str('cm'):
         break
     elif measure == str("in"):
         break
     else:
         measure =  input("please enter cm or in")
         continue

更好的是，为了避免使用break或continue，您可以使用以下内容，这会简化您的逻辑并考虑大小写：

measure = raw_input("what form of measurement do you want to use: (enter CM or IN): ").lower()

while measure != 'cm' and measure != 'in':
    measure = raw_input("please enter cm or in").lower()

Answer 2

以下代码是已经过测试的评论中代码的混搭

 measure = raw_input("what form of measurement do you want to use: (enter CM or IN): ")
 while True:
     if measure == 'cm':
         break
     elif measure == "in":
         break
     else:
         measure =  raw_input("please enter cm or in: ")
         continue

Answer 3

measure = raw_input("what form of measurement do you want to use:  (enter CM or IN): ")
b = True
while b:
     if measure == 'cm' or measure == "in":
         b = False
     else:
         measure = raw_input("please enter cm or in ")

只需将您的上一个input更改为raw_input

即可

Answer 4

缩进怎么样？不要忘记缩进是python知道的方式，如果你仍然在while / if / for / ...语句中。我没有在这里有一个python翻译，但我的猜测是，如果你正确缩进它应该有效。此外，使用while measure != "cm" and measure != "in"

等其他条件会更好

measure = raw_input("blablabla")
while measure != "cm" and measure != "in":
  measure =  raw_input("please enter cm or in: ")

Answer 5

您可以重新编写代码，以便只有一个数据提示。删除不需要的str次转化，使用大写字母进行测试，然后检查输入的值是否在所需值列表中。（并通过将字符串放在多行上来摆脱那种语法错误）

while True:
    measure = raw_input("what form of measurement do you want to use:"
    " (enter CM or IN): ").strip()
    if measure.upper() in ("CM", "IN"):
        break
    print("Incorrect input, try again")

（PYTHON）声明帮助2.7

5 个答案: