Is there a way to return literally nothing in python?

Question

I'm learning python and I was just wondering if I there was a way to write a code that does something like:

def f(x):
    if x>1:
       return(x)
    else:
        # don't return anything

I'm asking about the else part of the code. I need to not return anything if x<=1, returning None isn't acceptable.

Answer 1

To literally return 'nothing' use pass, which basically returns the value None if put in a function(Functions must return a value, so why not 'nothing'). You can do this explicitly and return None yourself though.

So either:

if x>1:
    return(x)
else:
    pass

or

if x>1:
    return(x)
else:
    return None

will do the trick.

Answer 2

There's nothing like returning nothing but what you are trying to do can be done by using an empty return statement. It returns a None.

You can see an example below:

if 'account' in command:
    account()

def account():
    talkToMe('We need to verify your identity for this. Please cooperate.')
    talkToMe('May I know your account number please?')
    acc_number = myCommand()
    talkToMe('you said your account number is '+acc_number+'. Is it right?')
    confirmation = myCommand()
    if confirmation!='yes' or 'correct' or 'yeah':
        talkToMe('Let\'s try again!')
        account()
    else:
        talkToMe('please wait!')
    return

This will return nothing to calling function but will stop the execution and reach to the calling function.

Answer 3

How about this?

def function(x):
     try:
         x = x+1
         return (x)
     except:
         return ('')

Answer 4

You can do something like this:

>>> def f(x):
...    return x if x>1 else None
... 
>>> f(1),f(2)
(None, 2)

It will appear to 'return nothing':

>>> f(1)
>>> 

But even the alternative returns None:

>>> def f2(x): 
...    if x>1: return x
... 
>>> f2(1),f2(2)
(None, 2)

Or:

>>> def f2(x):
...    if x>1: 
...        return x
...    else:
...        pass
... 
>>> f2(1),f2(2)
(None, 2)

So they are functionally the same no matter how you write it.

Answer 5

As mentioned above by others, it will always return None in your case. However you can replace it with white space if you don't want to return None type

def test(x):
    if x >1:
        return(x)
    else:
        return print('')

Answer 6

You can use lambda function with filter to return a list of values that pass if condition.

Example:

    myList = [1,20,5,50,6,7,2,100]
    result = list(filter(lambda a: a if a<10 else None, (item for item in myList)))
    print(result)

Output:

    [1,5,6,7,2]

Answer 7

I may have a tip for you ! Writing print(f(x)) will output None if there is no return value, but if you just call your function without the 'print', and instead write in the function some 'print(s)' you won't have a None value

Answer 8

you can use return chr(0) cause 0 in ASCII doesn't have a character hence it leaves it blank

Answer 9

Just to add to all the answers, the only actual way to not return a function is to raise an exception. At least, as long as the program needs to run even after not returning anything.

So your code can be:

def f(x):
    if x>1:
        return x
    raise Exception

(Note that I didn't use an else block to raise the Exception since it would have already returned the value if the condition was satisfied. You could, however, do this in an else block, too)

On test running:

num1 = f(2)    # 2
num2 = f(0)    # Unbound; and error raised

Now this can be useful if you want to also keep returning None an option for some conditions, and not returning anything for some other conditions:

def f(x):
    if x > 0:
        return x
    elif x == 0:
        return None  # pass
    raise Exception

>>> num1 = f(1)  # 1
>>> num2 = f(0)  # None
>>> num3 = f(-1) # Unbound; and error raised

---

If you don't want the program to exit and show an error, you can make it catch the exception outside of the function:

try:
    num = f(0)
except:
    pass

This way, if at all f(0) raises an exception (which it would) it will be caught be the except block and you can happily continue the program, being rest assured that num is not None, but simply unbound.

---

An interesting fact:

The only other way to not return anything is probably to simply exit the program, which is what exit() and quit() do. When I check the return type for exit() and quit() in my code editor, it shows me NoReturn, which is different from when it shows None for a regular function :)

Answer 10

In Simple Terms

for i in range(0,10):
    if i<5:
        None
    else:
       print("greater")

Output:-

greater
greater
greater
greater
greater

The code outputs nothing for all values less than 5.