Python:当我调用 "Sub"时，它不会到达

Question

我编写了这个简单的代码，试图演示我在使用 Python 时遇到的问题。这是代码:

def Main():
    print("In Main.")
    while(True):
        TheInput1 = input("Go To Sub?:")
        if(TheInput1.lower() == "y"):
            Sub()
            break
        elif(TheInput1.lower() == "n"):
            print("bye")
            quit()
        else:
            print("what?")
Main()
def Sub():
    print("In Sub");
    while(True):
        TheInput2 = input("Go To Main?:")
        if(TheInput2.lower() == "y"):
            Main()
            break
        elif(TheInput2.lower() == "n"):
            print("bye")
            quit()
        else:
            print("what?")
Sub()

每当我输入 y 时，它都会给我一个错误，而不是转到 Sub。这是错误:

Traceback (most recent call last):
  File "python", line 11, in <module>
  File "python", line 6, in Main
NameError: name 'Sub' is not defined

我确定解决方案非常简单，但我不知道如何实现。

Answer 1

您在定义 Sub 之前调用 main，将 main 调用移至 sub 下方。

def Main():
    print("In Main.")
    while(True):
        TheInput1 = input("Go To Sub?:")
        if(TheInput1.lower() == "y"):
            Sub()
            break
        elif(TheInput1.lower() == "n"):
            print("bye")
            quit()
        else:
            print("what?")
def Sub():
    print("In Sub");
    while(True):
        TheInput2 = input("Go To Main?:")
        if(TheInput2.lower() == "y"):
            Main()
            break
        elif(TheInput2.lower() == "n"):
            print("bye")
            quit()
        else:
            print("what?")
Main()
Sub()