Palindrome-inize a number

Question

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

• BusyAnt: First improvement I'd suggest is to use decent names for variables and methods, add comments, and skip fewer lines.
• Farhan.K: @BusyAnt I just realised that I pasted the wrong version of my code. The only thing different is that the newer one has more sensible variable names but still doesn't have comments/less blank lines. Thanks for pointing that out!

Answer 1

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