Question

下面解释了getvalidint函数，因为我调用函数getvalidint并给它一个输入，因此它可能产生一个整数输出。这不是因为我打印函数输出（见下面的主程序）它打印出“无”，我在python33上运行。

#getValidInt() takes in a minn and maxx, and gets a number from the
#               user between those two numbers (inclusive)
#Input:      minn and maxx, two integers
#Output:     an integer, between minn and maxx inclusive


MIN_VAL = -1000000
MAX_VAL =  1000000

def getValidInt(minn, maxx):
    message = "Please enter a number between " + str(minn) + " and " + \
        str(maxx) + " (inclusive): "
    newInt = int(input(message))
    while newInt <= minn & newInt >= maxx:

    # while loop exited, return the user's choice
        return newInt

def main():

    userNum = getValidInt(MIN_VAL, MAX_VAL)
    print(userNum)

main()

Answer 1

如果永远不会满足while newInt <= minn & newInt >= maxx:条件，则不会返回任何内容。这意味着该函数将隐式返回None。另外，假设您正在使用python 3（我从int(input())成语中引出）。

更深层次的问题是输入代码只会运行一次，无论该值是否满足约束条件。这样做的典型方式是：

import sys

def get_int(minimum=-100000, maximum=100000):
    user_input = float("inf")
    while user_input > maximum or user_input < minimum:
        try:
            user_input = int(input("Enter a number between {} and {}: ".format(minimum, maximum)))
        except ValueError:
            sys.stdout.write("Invalid number. ")
    return user_input

函数不生成整数，而是生成“无”输出

1 个答案: