Question

我是python的新手，我想知道如何在用户输入无效之前调用函数。这是一个代码示例：

start = input("For sum of squares, type 'squares'. For sum of cubes, type 'cubes'. "
              "\nIf you would like to raise a number to something other than 'squares' or 'cubes', type 'power'. "
              "\nIf you would like to exit, type 'exit':")

def main_function(start):
    while start.lower() != "exit":
        if start.lower() in "squares":
            initial = input("What is the initial constant for the sum of the squares: ")
            terms = input("Number of terms: ")

        if start.lower() in "cubes":
            initial = input("What is the initial constant for the the sum of the cubes: ")
            terms = input("Number of terms: ")



           if start.lower() in "power":
                initial = input("What is the initial constant for the the sum: ")
                terms = input("Number of terms: ")

        else:
            print("Program halted normally.")
            quit()

main_function(start)

我想让它做的是，如果用户输入正确的输入，则重新启动'start'，然后让它再次运行该功能。我已经尝试将'start'放在'else'语句上方和下方的函数中，但它从不接受新的输入。

Answer 1

我会这样做，在方法中定义开始输入并在循环内调用它，当它等于"exit"而不是打破循环。

同样使用elif，这样如果第一个条件语句为True，则不会检查其他条件语句，除非你当然想要这样。

def get_start_input():
    return input("For sum of squares, type 'squares'. For sum of cubes, type 'cubes'. "
              "\nIf you would like to raise a number to something other than 'squares' or 'cubes', type 'power'. "
              "\nIf you would like to exit, type 'exit':")

def main_function():
    while True:
        start = get_start_input()
        if start.lower() == "squares":
            initial = input("What is the initial constant for the sum of the squares: ")
            terms = input("Number of terms: ")

        elif start.lower() == "cubes":
            initial = input("What is the initial constant for the the sum of the cubes: ")
            terms = input("Number of terms: ")

        elif start.lower() == "power":
            initial = input("What is the initial constant for the the sum: ")
            terms = input("Number of terms: ")

        elif start.lower() == "exit":
            print("Program halted normally.")
            break

main_function()

修改

正如dawg在评论中写道，我们最好在==而不是in使用，因为你可以有几个匹配和含糊不清的含义。

如何在无效输入之前调用函数？

1 个答案: