Python：从函数返回时没有值

Question

I'm writing a program that stores 3 players and their scores in a list and then prints them out at the end. Simple stuff really, however I'm trying to call the value for the player score from a function called playerscore() which prevents you from entering a score >5.

this works fine when you run through it with the correct value, but if you input an incorrect value > 5 then it begins the playerscore function again and allows for a new value to be entered but returns "None"

teamlist = []

def playercreator():
    counter=0
    while counter < 3:
        name = playername()
        score = playerscore()
        print(score) #check - this one goes wrong when returned after the if/else in playerscore()
        teamlist.append(name+" "+str(score))
        counter = counter + 1

def playername():
    name=input("What name do you want for your player?\n")
    return (name)

def playerscore():
    global teamtotal
    score=input("input score?\n")
    print(score) #check
    if int(score)>5:
        print("Your attack score must be between 0 and 5")
        print(score) #check
        playerscore()
    else:
        return int(score)

playercreator()

for x in teamlist:
    print(x)

for example, these are the inputs and outputs:

What name do you want for your player?
p1
input score?
3
What name do you want for your player?
p2
input score?
6
Your attack score must be between 0 and 5
input score?
5
What name do you want for your player?
p3
input score?
2

p1 3
p2 None
p3 2

I feel like there's something obvious that i'm missing. Can anyone point me in the right direction?

Answer 1

You are missing a return statement in the if block (when the score is greater than 5):

def playerscore():
    global teamtotal
    score=input("input score?\n")
    if int(score)>5:
        print("Your attack score must be between 0 and 5")        
        return playerscore()
    else:
        return int(score)

Output:

What name do you want for your player?
shovon
input score?
2
2
What name do you want for your player?
sorida
input score?
23
Your attack score must be between 0 and 5
input score?
43
Your attack score must be between 0 and 5
input score?
234
Your attack score must be between 0 and 5
input score?
1
1
What name do you want for your player?
shody
input score?
2
2
shovon 2
sorida 1
shody 2

From official documentation :

In fact, even functions without a return statement do return a value, albeit a rather boring one. This value is called None (it's a built-in name).

Answer 2

When you are doing this:

if int(score)>5:
    playerscore()

you call playerscore function without return statement. This produces None value.

Answer 3

The type of recursion you're trying to do with your code will work with a small correction on your code... which follows:

def playerscore():
global teamtotal
score=input("input score?\n")
print(score) #check
if int(score)>5:
    print("Your attack score must be between 0 and 5")
    print(score) #check
    return playerscore()
else:
    return int(score)

You can notice that this time, we returned playerscore() . As it seems like you're learning the basics, I'd like to propose a slightly different approach, as you'll get a ValueError exception if the player types a string (some letters) instead of a number. You can keep using your recursive function in the exception catch, and use a while loop to make the player to keep the number within your desired range. Here follows my suggestion to prevent the ValueError exception:

def playerscore():
global teamtotal
score=input("input score?\n")
try:
    while int(score) < 0 or int(score) > 5:
        print("Your attack score must be between 0 and 5")
        print(score)  # check
        score = input("input score?\n")
except ValueError:
    print("Your attack score must be A NUMBER between 0 and 5")
    return playerscore()
return int(score)

I hope that helps. Regards.

Answer 4

When function doesn't return anything, value will be None .

So you should check your code for the case where score is larger than 5. (Compare it to the case where score is not larger than five.)