iv)List :

      List is the best of the data types in python3.

      It can hold anything(Literally anything).

      Syntax :

             There are two ways you can declare an empty list:

                          list() or []

            >>> type(list())

    <class 'list'>

    >>> type([])

    <class 'list'>

>>> [1,2,"string", """ multiline \n comment """, 12.564]

[1, 2, 'string', ' multiline \n comment ', 12.564]

>>> a = [2, 5, 45.74, "python"]

>>> a[0]

2

>>> a[3]

'Python'

Python has a special provision for accessing elements from last in case the length of list is unknown.

You can access the last element by using negative indexing.

List[-n] returns nth element counting reverse , starting from the last in the List  .

>>> a[-1]

'Python'

>>> a[-3]

5

Checking length(number of elements) of list :

    len(list) is the method used to find.

        >>> len(a)

4

 

Slicing in list :

    Slicing is a process of selection of elements by using indexes.

    List[a:b] will return list of elements in List from index a to b

        Excluding element at bth position. b>=a

    If a/b parameters are not provided then python takes extreme

        Position.

        For example :

>>> a[2:4]

[45.74, 'python']

>>> a[2:1]

[]

>>> a[3:]

['python']

>>> a[:3]

[2, 5, 45.74]

>>> a[:]

[2, 5, 45.74, 'python']

Slicing with negative index :

>>> a[:-1]

[2, 5, 45.74]

>>> a[:-2]

[2, 5]

a[-x ] is same as a[len(a) - x ]

>>> a[:-1]

[2, 5, 45.74]

>>> a[:-2]

[2, 5]

Reversing a list :

>>> a[::1]

[2, 5, 45.74, 'python']

    reversed(x) can be used to reverse a list.

    Rerversed function returns a reverseiterator . So, it has

        to be type casted to list.

>>> list (reversed(a))

['python', 45.74, 5, 2]

Counting occurrences of certain element in a list.

Syntax : list.count(element_to_find_frequency_of)

Example :

>>> [1, 1, 2, 1, 2, 5, 8 ,6, ""].count(1)

3

Sorting a list :

    sort attribute can be used to sort a list.

    To use sort attribute, list cannot have any other type other than

        that of int and float.

    sort attribute does not return anything but performs sorting on

        the list.

>>> a = [1, 2, 5, 4, 3]

>>> a.sort()

>>> a

[1, 2, 3, 4, 5]

Pop attribute of list :

Syntax : list.pop(index)

             Where, index is index of element you want to remove

             from the list.

This attribute returns the deleted element.

    [1, 3.23, 4, 5]

>>> a.pop(1)

3.23

>>> a

[1, 4, 5]

Copying a list :

    Suppose a=[1,2,3] is a list.

    b = a will give reference of a to b, not copying the list.

    Now, what does that mean??

    That means, when you will modify elements of a, elements of

        b will also be affected and vice versa.

    For copying the elements of a list to another, copy attribute is

        Used.

    b = a.copy()

    Now, elements in b will have elements same as a but

       modifying a or b won’t affect the other list.

Append attribute :

Append takes exactly one argument as an input that will

include the argument passed inside the attribute in the list.

>>> a

[1, 45, 3, 4, 5]

>>> a.append([1,2,3])

>>> a

[1, 45, 3, 4, 5, [1, 2, 3]]

Here, i append a list [1, 2, 3] to the list a.

Removing all the elements :

clear attribute is used.

        >>> a.clear()

>>> a

[]

List can be merged with another list using extend attribute of the list

list.extend(list1)

>>> a = [1, 2, 3, 5]

>>> a.extend([4, 6])

>>> a

[1, 2, 3, 5, 4, 6]

This is one of the way you can add a list to another list.

Another way is :

list = list + list1

>>> a = a + [9, 7, 8]

>>> a

[1, 2, 3, 5, 4, 6, 9, 7, 8]

These were some of the  attributes and functionalities you can do using list. 
More properties we will see in future posts.