Convert While Loop to For Loop in Python

Usin count() function in itertools module gives an iterator of evenly spaced values. The function takes two parameters. start is by default 0 and step is by default 1. Using defaults will generate infinite iterator. Use break to terminate loop.

import itertools
percentNumbers = [ ]
finish = "n"
num = "0"
for x in itertools.count() :
    num = input("enter the mark : ")
    num = float(num)
    percentNumbers.append(num)
    finish = input("stop? (y/n) ")
    if finish=='y':break
print(percentNumbers)

Sample output of the above script

enter the mark : 11
stop? (y/n)
enter the mark : 22
stop? (y/n)
enter the mark : 33
stop? (y/n) y
[11.0, 22.0, 33.0]