while循环正确嵌套

Question

我正在寻求关于正确使用以下3个while循环的帮助：

while choice is None:  ...
while not isinstance (choice, int):  ...
while int(choice) not in range(0,1):  ...

可能是这样的：

while choice is None and not isinstance (choice, int) and int(choice) not in range(0,1):
    print("Invalid option!")
    choice = input("Choose key: ")

我该如何正确地嵌套它呢？

choice = None
choice = input("Choose key: ")

while choice is None:
    choice = input("Choose key: ")

while not isinstance (choice, int):
    print("choice is an integer and I equal 0 or 1")
    print("Also if I am None or not an int, I will loop until I meet I am")

while int(choice) not in range(0,1):
    choice = input("Choose key: ")
    choice = int(choice)

Answer 1

您可以通过将所有内容移动到一个循环中来很好地压缩这些内容：

while True:
    choice = input("Choose key: ")
    if choice in ("0", "1"):
        choice = int(choice)
        break

Answer 2

input返回一个str对象period。它永远不会返回None，它永远不会返回int。只需(尝试)将choice转换为int，然后检查结果值，只有在输入0或1时才会中断。

while True:
    choice = input("Choose key: ")
    try:
        choice = int(choice)
    except ValueError:
        continue
    if choice in (0, 1):
        break

Answer 3

如果你需要一个整数输入...

while True:
    try:
        choice = int(input('Enter choice: '))
    except ValueError:
        print('Invalid choice')
    else:
        # add an if statement here to add another condition to test the int against before accepting input
        break
# .... do whatever next with you integer