Original subtitles

0 To calculate the average of these grades we want to see if a list type has some sort of mean or average 1

method that allows us to get the average of its values. 2

For that we go to check with dir list. 3

So list is the name that represents all lists. 4

So that is the type. 5

And this is an instance of that type, of the list type. Dir list and let's have a quick look here. 6

Do we have a mean or average method? 7

I don't think, so so there's no methods of the list type to allow us to calculate the average of a list 8

values. 9

However that doesn't mean that it doesn't exist 10

a mean method in Python to do that. Mean or average 11

it's not a method, but it can be a function. 12

You remember the print function so print like that. 13

You see that print doesn't need the dot notation to be used like for example the upper method did need 14

a dot notation because upper is a method attached to the HELLO type and print is a function, it is an 15

independent function that works with many types, not only strings, not only integers, float. 16

You can print anything with print. 17

That's why it's not attached to a specific type. 18

So where do we see a complete list of functions that we can use. 19

You can do that using dir again underscore underscore built ins underscore underscore close parentheses. 20

And that is 21

a complete list of what you can use built in functions and also types in Python because here you also 22

see like the list word that we used an str, and that's basically what Python has 23

in a nutshell so these functions, and the methods of the types such as str, and least and so on. 24

These are actually the built in features of Python. 25

What comes with the Python installation. 26

We will see later that there are also libraries made by other people for example to process images. 27

To process pixels of an image. 28

Python doesn't have that because that that'd be too much to be included in the Python 29

default installation so people have come up with libraries which are still Python codes and we'll look 30

at that later. 31

So this external Python code that you can install as an add on, as an extension will allow you to make 32

more operations, but the built in Python is this basically. 33

So let me see for a mean function, or an average function. 34

No, it's not there. 35

Okay but there is a some function. 36

So what we can do is, let's say my sum, don't use sum as a variable name because you can see that sum 37

is a reserved keyword. 38

So sum(student_grades), that will give us the sum of these three numbers, and then we want to count how many 39

items there are in that list. 40

So do we have a count something there? 41

Maybe not. 42

Well I know that there's no count method but we have this Len. 43

Which means... You can check what it means. 44

So return of the number of items in a container. 45

So a list is also referred to as a container. 46

Let's say a length equal to Len. 47

Student grades. 48

And then finally we can get the mean which is my sum divided by length and printout the mean, save and 49

that is the mean value of all those three numbers.