Control Flow - While Loops
The while statement iterates (repeats) the same code block as long as certain condition is met. Iteration means executing the same block of code over and over. A code that implements iteration is called a loop. Python has two primitive loop commands:
|while loops||Indefinite iteration||The number of times the loop is executed isn’t specified explicitly in advance|
|for loops||Definite iteration||The number of times the designated block will be executed is specified explicitly at the time the loop starts|
Before every iteration the while condition is calculated. If True - the block beneath the command is executed.
Here is an example:
#while x = 1 while x < 5: print(x) x += 1 print("loop ended")
Here is a diagram describing the process:
The continue Statement
Using the continue statement we can skip the current iteration, and continue to the next one:
#continue x = 0 while x < 5: x += 1 if x == 3: continue print(x)
The break Statement
Using the break statement we can exit the loop (not just one iteration):
#break x = 1 while x < 5: if x == 3: break print(x) x += 1
The else Statement
Using the else statement we can run code when the condition is False:
#else x = 1 while x < 5: print(x) x += 1 else: print('While loop is a great tool')
Nested while Statements
It is possible to use a nested while statement:
#nested while x = 1 while x < 10: print(x) while x < 3: print("We are at the very beginning") x += 1 else: print('While loop is a great tool')
- Define a variable with the value of 2.
- Create a while loop that runs as long value equals less than 20.
- Inside the loop print the variable and add 2 to the variable.
#Write your code here: