Python Tutorial #3|Lists

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 square brackets. For example:

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

NOTE: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]
print (list1[1:3])

OUTPUT:

['chemistry', 1997]

Updating List:

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] = 2001Value available at index 2 :
1997

OUTPUT:

New value available at index 2 :
2001
print ("New Value available at index 2 : ")
print (list[2])

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)

OUTPUT:

['physics', 'chemistry', 1997, 2000]
After deleting value at index 2 :
['physics', 'chemistry', 2000]