palindrome

palindrome.py

#!/usr/bin/env python
# Write a method palindrome_chain_length which
#  - takes a positive number and
#  - returns the number of special steps needed to obtain a palindrome.
# The special step is:
#  - "reverse the digits, and add to the original number".
# If the resulting number is not a palindrome,
#   repeat the procedure with the sum
#   until the resulting number is a palindrome.
# 
# If the input number is already a palindrome, the number of steps is 0.
# 
# Input will always be a positive integer.
# 
# For example, start with 87:
# 
# 87 + 78 = 165; 165 + 561 = 726; 726 + 627 = 1353; 1353 + 3531 = 4884
# 
# 4884 is a palindrome and we needed 4 steps to obtain it, so palindrome_chain_length(87) == 4

import sys

def is_palindrome(num):
    if num == int("".join(reversed(str(num)))):
        return True
    return False
    
def palindrome_chain_length(num, steps=0):
    #print(f'Steps are now: {steps}')
    #print(f'Number is now: {num}')
    if is_palindrome(num):
        return (num, steps)
    steps += 1
    # Reversing the number
    mun = int("".join(reversed(str(num))))
    num += mun
    r = palindrome_chain_length(num, steps)
    return (r[0], r[1])

def main():
    if len(sys.argv) != 2:
        print("Wrong number of arguments, expected exactly 1")
        sys.exit(1)
    num = int(sys.argv[1])
    print(f'Received: {num}\nCalculating...')
    pal = palindrome_chain_length(num)
    print(f'Palindrome is {pal[0]}, after {pal[1]} steps')


if __name__ == "__main__":
    main()