Question

如何在python中创建多个不等式？例如。

school_type = input ("Enter what type of school you want. press H for high school, M for middle school, or E for elementary school").lower()

while school_type != "h" or school_type != "m" or school_type != "e": # Is this code correct?

   print ("You must enter H, M, or E")

Answer 1

school_type != "h" or school_type != "m"将始终评估为True，因为school_type将始终不等于"h"或不等于"m"。

您应该在while-loop条件中使用and而不是or：

while school_type != "h" and school_type != "m" and school_type != "e":

那，或者您可以使用not in：

while school_type not in {"h", "m", "e"}:

Answer 2

正如@iCodez所说，如果school_type与"h"不同，并且与"m"不同，而且与"e"不同，则需要再次进行迭代。正如他所说，用school_type not in ["h", "m", "e"]之类的东西可以更好地表达出来。该表达式更简单，更易于阅读且不易出错。

更改while条件后，我仍然会在代码中修复两件事。首先，如果条件为真，即用户为school_type键入了错误的值，则应采取适当的操作：必须要求用户键入新值，直到他/她键入正确的值为止。其次，您应该使用raw_input()而不是input()。区别在于第一个更适合字符串，而第二个是有问题的，在这种情况下实际上需要用户在输入值周围键入"。

结果可能是这样的：

def ask_for_school_type():
    s = "Enter what type of school you want. Type H for high \
school, M for middle school, or E for elementary school: "
    return raw_input(s).lower()

school_type = ask_for_school_type()
while school_type not in ["h", "m", "e"]:
   print "You must enter H, M, or E"
   school_type = ask_for_school_type()

如何制作多重不等式？

2 个答案: