如何只接受3-8之间的整数而不接受字符串？ （Python 2.7.5）

Question

I'm trying to make a function that asks for an integer between 3-8 and will continue asking until the user inputs an integer between 3-8. So it will ask again if you enter 0, -1, 9 or "rabbits".

So far I have this:

def GetNumberOfColours():
    NumberOfColours = None
    while type(NumberOfColours) != int or int(NumberOfColours) < 3 or int(NumberOfColours) > 8:
        print "Please enter the amount of colours you would like to play with (min 3, max 8)."
        NumberOfColours = raw_input()
    NumberOfColours = int(NumberOfColours)

But this code at the moment won't work as it takes the raw input and won't see it as an integer if it is. But if I use input() then it won't accept a string which could be input and stop the code. How can I make this work?

Answer 1

type(NumberOfColours) will always be str (or NoneType in the very first run) because raw_input() returns a string.

You should be doing it like this:

def get_number_of_colours():
    while True:
        print "Please enter the amount of colours you would like to play with (min 3, max 8):",
        try:
            num_colours = int(raw_input())
        except ValueError:  # gets thrown on any input except an integer value
            continue
        if 3 <= num_colours <= 8:
            return num_colours

Answer 2

You need to indent the last line to have the script repeatedly convert the input to an integer.

You'll then discover that entering "rabbits" will produce a ValueError as int() can't convert that to a number. This can be handled with a try/except :

def GetNumberOfColours():
    NumberOfColours = None
    while type(NumberOfColours) != int or int(NumberOfColours) < 3 or int(NumberOfColours) > 8:
        print "Please enter the amount of colours you would like to play with (min 3, max 8)."
        NumberOfColours = raw_input()
        try:
            NumberOfColours = int(NumberOfColours)
        except ValueError:
            NumberOfColours = None

Answer 3

将此用于您的while行：

while !NumberOfColors.isDigit() or int(NumberOfColours) < 3 or int(NumberOfColours) > 8: