pyCollatz

# collatz Python exercise
# Mike Kerry Dec 2020

def collatz(number):
    if not number & 1:          # bit-wise test for even
        return number >> 1      # >> 1 integer divides by 2
    return 3 * number + 1       # number was odd


while True:
    mystr = input("Type a number: ")    # input as a string
    if mystr.isdigit():                 # if the input is an integer ...
        break                           # break out of while loop
    print("Invalid number, try again")  # report invalid input and loop again

y = int(mystr)              # convert input string to an integer
while y != 1:               # Keep looping until y is 1
    y = collatz(y)          # pass y to the function, and assign the return value to y
    print(y)                # print y each time around loop