valid_input.py

def valid_input (validator=str, prompt="", accept=None, reject=[], persist=True, apply=None):
    while True:
        try:
            response = validator(input(prompt))
            normalized = apply(response) if apply != None else response
        except ValueError:
            if persist != False:
                print("Invalid input!")
            else:
                return None
        except KeyboardInterrupt:
            print("\nInput canceled!")
            return None
        else:
            if (accept == None or normalized in accept) and normalized not in reject:
                return response
            elif persist != False:
                print("Invalid input!")
            else:
                return None

valid_input_example.py

# Returns only if an valid integer was input
response = valid_input(int)

# Returns only if an valid string was input and in lowercase
response = valid_input(str.lower)

# Returns only if "yes" or "no" was input;
response = valid_input(str, "Test str input: ", ["yes", "no"])

# Returns if exactly "y" or "yes" was input, otherwise it returns None;
response = valid_input(str, "Test str input: ", ["y", "yes"], persist=False)

# Returns if uppercase "Y" or "YES" was input, otherwise it returns None;
response = valid_input(str, "Test str input: ", ["Y", "YES"], apply=str.upper)

# Returns if not "foo" or "bar" was input, otherwise it returns None;
response = valid_input(str, "Test str input: ", reject=["foo", "bar"])

# Returns only if valid integer that is 1, 3 or 5 was input;
response = valid_input(int, "Test int input: ", [1, 3, 5])

# Returns only if an valid integer between 1 and 9 was input;
response = valid_input(int, "Test int input: ", range(1, 10))

# Returns only if an valid float was input;
response = valid_input(float, "Test float input: ")

Wow, Amazing!