LISTS in Python

One of the basic data structures in Python is sequences. There are six built-in types of sequence - strings, Unicode strings, lists, tuples, buffers, and xrange objects. The most common are lists and tuples.

 A list is an ordered set of values, where each value is identified by an index. The values in the list are known as elements. Each element of a sequence is assigned with a number - its position or index. The first index is zero, second is one and so forth.

Creation and Accessing List:

The list can be created by putting values separated by commas between square brackets []. List is one of the most freuently used and very versatile data type used in Python. 

Syntax for List:

               <List_name> = [<Value_1>,<Value_2>,........,<Value_N>]

NOTE: Nested lists are also acceptable.

List Operations:

Two operations + and * is allowed in list. + for concatenation of lists and * repeats the list elements a given number of times.

Try Yourself:

Nos_List = [1,2,3]

Char_List = ["a","b"]

#add two lists

Add_list = Nos_list + Char_List

#Append same elements n no.of times

Repeat_List = Char_List * 3

print "Add_List : ", Add_List

print "Repeat_List : ", Repeat_List

List Slices:

A subsets of elements of a list is known as slice of list. Selecting a list slice is similar to selecting a character in a string.

Try Yourself:
Nos_list = [1,2,3,4,5,6,7,8,9,10,11]

#different slicing of list
print "Elements 3rd to 5th : ", Nos_list[2:5]
print " Elements beginning up to -5th index : ", Nos_list[:-5]
print "Elements from 5th to end : ", Nos_list[5:]
print "Elements from beginning to end : ", Nos_list[:]

List Methods:

The list datatypes has some methods. Methods that are available for the list object in Python Programming are tabulated as follows:

The following table gives the result of every method for the considered list. in general the methods are accessed as ListVariable.MethodName().

S.No	Method	Description
1.	append(E)	Add a an element(E) to the end of the list.
2.	extend(seq)	All elements of the list to another list(seq).
3.	insert(ind,E)	Insert an element(E) at the defined index(ind).
4.	remove(E)	Removes the first occurrence of the element (E) from the list.
5.	pop(ind)	Removes and returns the element at the given index(ind).
6.	index(E)	Returns the index of the first matched element with E.
7.	count(E)	Returns the count of number of elements (E) in the list.
8.	sort( )	Sort items in a list in ascending order.
9.	reverse( )	Reverse the order of items in the list.
10.	copy( )	Returns the shallow copy of the list.