Original subtitles

0 Something to point out is that when your function doesn't have a return statement, save, execute. 1

it implicitly returns a None object. 2

None is a specific object in Python which means nothing. 3

It's not an integer. 4

It's not a float. 5

It's not a string. 6

It's just None, it means nothing. 7

So Python what it does is if it doesn't find the return statement on the background it does this: 8

return None. 9

So if you execute that, ups an indentation error. 10

That's a good thing. 11

So you see that all this block here has to be the same level of indentation, if indented four lines here, 12

you have to indent for lines in here too. 13

So indentation has to be consistent. 14

That looks all right. 15

So we got the same outputs, None here and None there. 16

Some people do this mistake instead of returning, they do... 17

They use print instead of using return they use a print function. 18

The mean which works half the way. 19

So it still returns the value. 20

And it also returns None. 21

So what's going on here is that when you call the function here Python will execute all these lines 22

so it calculates the mean. 23

Then it goes to the next line so line by line it will print the mean. 24

So it will print out the mean in here and then it will look for a return statement. 25

It doesn't find it so it will return None. 26

The problem with this is that if you try to do some other operations with your mean value let's say 27

my mean is equal to the mean function 0, 3, and 4. 28

OK. 29

And I want to print out my mean plus 10. 30

So I would expect that this would give me the value of 7 is the sum divided by 3. 31

So two point something plus ten, twelve point something, but let's see what this will give me. 32

So this will give me a type error instead. 33

It's tried to add the None type which is None. 34

So this is a None type. 35

That's the type of this value. It's trying to add that to 10. 36

So my mean is None because it's returns None, and the interpreter will try to add up 37

that to 10. 38

That's not possible. 39

So that's why you shouldn't use print. 40

If I replace that with return instead, remove the parentheses, save, execute, that will give me 41

12.3. 42

That is the average plus 10. 43

However this doesn't mean you can not use print in your functions. 44

You can actually do that. 45

Let's say you just wants to print some information. 46

Started, functions started and execute that. 47

So you get the output of print in here, and then Python returns the mean, so you get the mean, 48

you store it in here, the output 49

of your function, but the value of the function is always what's you return in here. 50

So if you see that. 51

So always use return in your functions unless you have a very special reason to do so.