Python programming language allows to use one loop inside another loop. Following section shows few examples to illustrate the concept.
for iterating_var in sequence: for iterating_var in sequence: statements(s) statements(s)
The syntax for a nested while loop statement in Python programming language is as follows −
while expression: while expression: statement(s) statement(s)
A final note on loop nesting is that you can put any type of loop inside of any other type of loop. For example a for loop can be inside a while loop or vice versa.
The following program uses a nested for loop to find the prime numbers from 2 to 100 −
#!/usr/bin/python i = 2 while(i < 100): j = 2 while(j <= (i/j)): if not(i%j): break j = j + 1 if (j > i/j) : print i, " is prime" i = i + 1 print "Good bye!"
When the above code is executed, it produces following result −
2 is prime 3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime Good bye!