While loop is the simplest loop of a language. This loop executes one or more statement while the given condition remains true. It is useful when the number of iterations is not known in advance.
while(condition) Statement Statement
x = 5 while x > 0: print "This Is No",x x = x-2
This Is No 1
This Is No 2
This Is No 3
This Is No 4
This Is No 5