谁能告诉我我的功能出了什么问题？

Question

I'm working on this project and I keep getting this problem when the code tries to return the "guess" variable, instead of returning the value of "guess" it goes to line 9 which converts the value into a string for some reason, and then returns that. when I go to use the returned value in something, Python says that the value is "NoneType".

def ask_question(max_length, rowOrCol, guessNumber):
    guess = raw_input("What is the "+rowOrCol+" number of your "+guessNumber+" guess? ")
    try:
        guess = int(guess)
        if guess <= max_length:
            return guess
        else:
            print "That number was too big, it must be no larger then " +str(max_length)
            ask_question(max_length, rowOrCol, guessNumber)
    except(TypeError):
        print "Only numbers are accepted, please try again!"
        ask_question(max_length, rowOrCol, guessNumber)

I call the function with this line:

first_guess_row = ask_question(4, "row", "first")

Is there anything that I'm missing?

Answer 1

of course all your branches need to return....

...
        else:
            print "That number was too big, it must be no larger then " +str(max_length)
            return ask_question(max_length, rowOrCol, guessNumber)
    except(TypeError):
        print "Only numbers are accepted, please try again!"
        return ask_question(max_length, rowOrCol, guessNumber)

before you were recalling the function ... but you were throwing away its return value

Answer 2

for lines 9 and 12, you are doing a recursive call.

A recursive call is a brand new call to the function within the function. The new call to ask_question, assuming line 6 is executed, is returning a value. but it is returned within the original ask_question call.

Therefore you need to change

ask_question(max_length, rowOrCol, guessNumber)

on line 9 and 12 to

return ask_question(max_length, rowOrCol, guessNumber)

to retrieve that value.

Another Note : recursive calls use extra memory for each recursion, which can cause slowdowns or even crash python (if you recurse a lot, depending on the size of the function). I would recommend putting your code into a loop like this:

continue_asking = True
while continue_asking:
    guess = raw_input("What is the "+rowOrCol+" number of your "+guessNumber+" guess? ")
    try:
        # typecheck the guess value
        guess = int(guess)
    except (TypeError):
        print "Only numbers are accepted, please try again!"
        continue

    if guess <= max_length:
        return guess
    else:
        print "That number was too big, it must be no larger then " +str(max_length)

Answer 3

Here's another method without using recursive function calls.

def ask_question(max_length, rowOrCol, guessNumber):
    while True:
        try:
            guess = int(raw_input("What is the "+rowOrCol+" number of your "+guessNumber+" guess? "))
            if guess <= max_length:
                return guess
            else:
                print "That number was too big, it must be no larger then " +str(max_length)
        except(ValueError):
            print "Only numbers are accepted, please try again!"