Palindrome-inize a number

For example if I start with the number 146. I first reverse it, so it becomes 641. Then I add this to the original number to make 787 which is a palindrome. I would repeat the process if the answer is not a palindrome.

I made this program show how long it ran for when it finishes or is interrupted and also to write the output to a file called output.txt.

from sys import exit from signal import SIGINT, signal from timeit import default_timer   def n(x):      counter = 0     b = 0     start = default_timer()      def t(*args):          end = default_timer()         total = end - start         print (total)          with open('output.txt','w') as f:              f.write('{}\n{}\n{}'.format(b, counter, total))          exit(0)      signal(SIGINT,t)       while True:          b += int(str(x)[::-1])          if b == int(str(b)[::-1]):              end = default_timer()             print (b, counter)             t()             break          else:              counter += 1             print (b,counter)             x = b 

Replay

A few notes:

  • A more pythonic way to determine if a given value is a palindrome:
    str(n) == str(n)[::-1]
    
    

    You do something similar in your code, but are converting from a string back to an int. This is more readable to me.

    However, this can slow down the code if we do this sort of casting a lot, so it would be better to abstract this functionality to a loop to reduce the number of casts and further increase readablity:

    def is_palindrome(num):
        string = str(num)
        return string == string[::-1]
    
    
  • Use the palindrome test as a check with the while loop
  • In the while loop, use the logic you already have to add on a reversed int:
    n += int(str(n)[::-1])
    
    
  • I would make it easier to input a number for the code to use, I did this with argparse.
    def get_args():
        parser = argparse.ArgumentParser(description=
            'Generate palindrome from number when added to its reverse')
        parser.add_argument('num', type=int, help='number for palindrome generator')
        return parser.parse_args()
    
    
  • Right now you are writing just a snippet of data to a file, but it is being overwritten every time. I'd recommend just outputting to stdout with this current method, or changing it so you append to a file instead of overwrite it. I've gone with the former recommendation in my final code.
  • For profiling and timing code, it's recommended you use a Python profiler instead of writing code yourself.

Final Code

import argparse

def get_args():
    parser = argparse.ArgumentParser(description=
        'Generate palindrome from number when added to its reverse')
    parser.add_argument('num', type=int, help='number for palindrome generator')
    return parser.parse_args()

def is_palindrome(num):
    string = str(num)
    return string == string[::-1]

def main():
    args = get_args()
    while not is_palindrome(args.num):
        args.num += int(str(args.num)[::-1])

    return args.num

if __name__ == "__main__":
    print(main())

Test run:

$ python test.py 146
787

Category: python Time: 2016-07-28 Views: 0

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