The while statement is used for repeated execution as long
as an expression is true:
while_stmt: "while" expression ":" suite
["else" ":" suite]
This repeatedly tests the expression and, if it is true, executes the
first suite; if the expression is false (which may be the first time it
is tested) the suite of the else clause, if present, is
executed and the loop terminates.
A break statement executed in the first suite terminates the
loop without executing the else clause's suite. A
continue statement executed in the first suite skips the rest
of the suite and goes back to testing the expression.