Lists

Ok! So lets talk about lists in Python.

Lists is one of the type of python objects. I have talked about python classes,objects and methods here. I will just explain about it here briefly:
Briefly everything in python is an object. And an object is of different type(like: list, string, float, numpy array). So list is just one of the type of python object.

INITIALIZATION of a List

lets initialize a variable x to a list:

                                                   x = [1,"Rahul",2,"Ram",3]

Note that, a list can contain different types as well(here,1 is an int while "rahul" is a string).

lets take a look at list of lists:

                                                y = [["liz",1.73],["emma",2.68]]

We can see the type by using type() function:

                                                      type(x)  OR   type(y)

this gives list as python object type.

SLICING of a List

To select first element of a list:

                                                   x[0]  

                                                 gives 1.

Remember: Indexing starts from 0 in python. So here, index of 1 is 0.

                                                                                             index of "Rahul" is 1. and so on.

                                                                               Also,      Index of last element is -1

                                                                                             Index of 2nd last element is -2 . and so on.

To select multiple elements of the list:

                                                x[1 : 4]

                                                 gives ["Rahul",2,""Ram"] 

NOTE THAT: element at index 4 is excluded.

Doing this:     x[1 : ]

                      gives ["Rahul",2,"Ram",3] 

Similarly,         x[: 2]

                      gives   [1,"Rahul"]   
                        

For Lists of list

                   y[0] gives ["liz",1.73]

  

To select "liz":

                                             y[0][0]  gives "liz"

To select 2.68:

                                           y[1][1]  gives 2.68