A loop statement allows a program to execute statements(s) repeatedly under a given condition. This enables a programmer to write Python programs in fewer lines of code and enhance the code readability. In Python, there are two types of loop statements.
The While loop allows a set of statements to be executed repeatedly until a given condition is true. It can be viewed as a repeating if statement. A while loop is preferred over for loop whenever number of iteration is not known beforehand.
while condition: statements
In below mentioned example, program uses while loop to sum all integers from 1 to 5.
sum = 0 i = 1 while (i < 6): sum = sum + i i = i+1 print(sum)
The else block can be used with while loop also. The else block is executed when condition check in while loop returns false.
while condition: statements else: statements
In below mentioned example, else code block is executed after exiting from while loop.
i = 1 while (i < 6): print(i) i = i + 1 else: print('loop exhausted.')
1 2 3 4 5 loop exhausted.
However, when program exits from while loop using break statements, it ignores the else block.
i = 1 while (i < 6): print(i) i = i + 1 if (i==4): break else: print('loop exhausted.')
1 2 3