Python Language While Loop


A while loop will cause the loop statements to be executed until the loop condition is falsey. The following code will execute the loop statements a total of 4 times.

i = 0 
while i < 4:
    #loop statements
    i = i + 1

While the above loop can easily be translated into a more elegant for loop, while loops are useful for checking if some condition has been met. The following loop will continue to execute until myObject is ready.

myObject = anObject()
while myObject.isNotReady():

while loops can also run without a condition by using numbers (complex or real) or True:

import cmath

complex_num = cmath.sqrt(-1)
while complex_num:      # You can also replace complex_num with any number, True or a value of any type
    print(complex_num)   # Prints 1j forever

If the condition is always true the while loop will run forever (infinite loop) if it is not terminated by a break or return statement or an exception.

while True:
    print "Infinite loop"
# Infinite loop
# Infinite loop
# Infinite loop
# ...