Question

我不能让我的while循环在getClasses函数结束时应该结束。 getNum和counter都设置为整数。我也试过做while True和一个if语句来看看这是否会有所帮助，但这只会给我一个无限循环。我知道这是一个简单的问题，但我无法弄清楚我做错了什么。请帮忙。

def getNum():
    while True:
        try:
            num = int(raw_input("How many classes do you have:\n")) #Asks the user for the number of classes he/she has.
            break
        except:
            print("Input must be a number")
    return num

def getGrades(): #Gets the grades from the user
    counter2 = 1
    global grades
    if counter2 <= getNum: #If the 2nd counter is less than or equa to the number of classes...
        while True:
            try:
                grades = int(raw_input("What is the grade for class %s:\n" %counter2)) #Asks the user what their grades are for 'counter' class.
                counter2 += 1 #...increase the 2nd counter by 1
                break
            except:
                print("Input must be a number")
     return grades

def getClasses(): #Gets the user's classes
    counter = 1
    getNum()
    while counter <= getNum: #If the counter is less than or equal to the number of classes...
        classes = str(raw_input("Class %s is what:\n" %counter)) #Asks the user what their 'counter' class is.
        subjects[classes] = getGrades()
        counter += 1 #...increase the counter by 1 
    return subjects

Answer 1

第4行，你的意思是这个？

if counter2 <= getNum() :
    ...

Answer 2

在except子句后命名异常。在这种情况下是一个ValueError。

如果在执行try子句期间发生异常，则其余部分该条款被跳过。然后，如果其类型匹配名为的异常在except关键字之后，执行except子句，然后执行在try语句之后继续执行。

源 https://docs.python.org/3/tutorial/errors.html

def getGrades():
    while True:
        try:
           grades = int(input())
           break
        except ValueError:
           print("Please enter digits only")
    return grades
getGrades()

在python中无限循环

2 个答案: