Python while Loop
The while statement allows us to repeatedly execute a block of statements as long as a condition is true
Indentation and Colon should be respected.
while test_expression: statement(s) must be indented
In while loop, test expression is checked first. If
test_expression is evaluates
then the statements within the body of loop executes.After one iteration, the test expression is checked again.
This process will continues until the
test_expression evaluates to
Python interprets any
non-zero value as
0 are interpreted as
Flow chart of while loop
count = 0 while (count < 9): print("The count is:", count) count = count + 1 print("Good bye!")OUTPUT
The count is: 0 The count is: 1 The count is: 2 The count is: 3 The count is: 4 The count is: 5 The count is: 6 The count is: 7 The count is: 8 Good bye!
The block here, consisting of the print and increment statements, is executed repeatedly until count is no longer less than 9. With each iteration, the current value of the index count is displayed and then increased by 1.
Example :Program to add natural numbers upto n
# To take input from the user, # n = int(input("Enter n: ")) n = 10 # initialize sum and counter sum = 0 i = 1 while i <= n: sum = sum + i i = i+1 # update counter # print the sum print("The sum is", sum)OUTPUT
Enter n: 10 The sum is 55
while loop with else :
Python supports to have an else statement associated with a loop statement.
If the else statement is used with a while loop, the else statement is executed when the condition becomes false.
The while loop can be terminated with a break statement. In such case, the
elsepart is ignored. Hence, a while loop's
elsepart runs if no break occurs and the condition is false.
counter = 0 while counter < 3: print("Inside loop") counter = counter + 1 else: print("Inside else")OUTPUT
Inside loop Inside loop Inside loop Inside else
Next topic is for Loop
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