Return integer type user input

def get_int(self, input_string):
        """
		Return integer type user input
		"""

        if input_string in ('--ensemble_size', '--ncpu'):

            # was the flag set?
            try:
                index = self.args.index(input_string) + 1
            except ValueError:
                # it wasn't, so if it's required, exit
                if input_string in self.required:
                    print("\n {flag} is required\n".format(flag=input_string))
                    print_short_help()
                    sys.exit(1)
                # otherwise return the appropriate default
                else:
                    return None

            # the flag was set, so check if a value was set, otherwise exit
            try:
                if self.args[index] in self.flags:
                    print("\n {flag} was set but a value was not specified".format(flag=input_string))
                    print_short_help()
                    sys.exit(1)
            except IndexError:
                print("\n {flag} was set but a value was not specified".format(flag=input_string))
                print_short_help()
                sys.exit(1)

            # a value was set, so check if its the correct type
            try:
                value = int(self.args[index])
            except ValueError:
                print("\n {flag} must be an integer".format(flag=input_string))
                print_short_help()
                sys.exit(1)

            # verify the value provided is not negative
            if value < 0:
                print("\n {flag} must be an integer greater than 0".format(flag=input_string))
                print_short_help()
                sys.exit(1)

            # everything checks out, so return the value
            return value