Nested Loops

A loop may contain another loop inside it. A loop inside another loop is called a nested loop. The inner or outer loop can be any type, such as a while loop or for loop. For example, the outer for loop can contain a while loop and vice versa. The outer loop can contain more than one inner loop. There is no limitation on the chaining of loops. Nested loops are typically used for working with number and star pattern programs.

 These are also useful to work with multidimensional data structures, iterating a list that contains a nested list. 

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

for x in li: #x values are [1,2,3] , [4,5,6]

for y in x: #y values are 1,2,3,4,5,6

print (y)