Lists in python

The list is a most versatile datatype available in Python which can be written as a list of comma-separated values (items) between square brackets. Good thing about a list is that items in a list need not all have the same type.

Creating a list is as simple as putting different comma-separated values between squere brackets. For example:

list1 = ['physics', 'chemistry', 1997, 2000]
list2 = [1, 2, 3, 4, 5 ]
list3 = ["a", "b", "c", "d"]

Like string indices, list indices start at 0, and lists can be sliced, concatenated and so on.

Accessing Values in Lists:

To access values in lists, use the square brackets for slicing along with the index or indices to obtain value available at that index. Following is a simple example:

list1= ['physics', 'chemistry', 1997, 2000]
list2 = [1, 2, 3, 4, 5, 6, 7 ]
print "list1[0]: ", list1[0] 

When the above code is executed, it produces the following result:

list1[0]:  physics

Updating Lists:

You can update single or multiple elements of lists by giving the slice on the left-hand side of the assignment operator, and you can add to elements in a list with the append() method. Following is a simple example:

list
= ['physics', 'chemistry', 1997, 2000]; print "Value available at index 2 : " print list[2] list[2] = 2001 print "New value available at index 2 : " print list[2]

Note: append() method is discussed in subsequent section.

When the above code is executed, it produces the following result:

Value available at index 2 :
1997
New value available at index 2 :
2001

Delete List Elements:

To remove a list element, you can use either the del statement if you know exactly which element(s) you are deleting or the remove() method if you do not know. Following is a simple example:

list1= ['physics', 'chemistry', 1997, 2000] 
print list1 del list1[2] 
print "After deleting value at index 2 : " print list1

When the above code is executed, it produces following result:
['physics', 'chemistry', 1997, 2000] After deleting value at index 2 : ['physics', 'chemistry', 2000]