Reversing an integer in python is not working

Question

def intreverse(n):   #reverses an integer
    x=0
    d=0
    while(n>0):
        d=n%10
        x=x*10+d
        n=n/10
    return x

Why is this code not giving me the reverse of an integer in python?

What version of Python do you use? In Python-3, n/10 is floating-point division, not integer division. — DYZ
– DYZ, Commented Feb 7, 2017 at 5:03
@JulienBernu For practical purposes, you can. For pedagogic, you cannot. But then, nobody would reverse an integer for any practical purpose. — DYZ
– DYZ, Commented Feb 7, 2017 at 5:05
@ArkaBhowmick, keep in mind that you should validate the answer if it was useful according to this — lmiguelvargasf
– lmiguelvargasf, Commented Feb 7, 2017 at 5:36

lmiguelvargasf · Accepted Answer · 2017-02-07 05:11:22Z

3

If you are using Python 3, use integer division // since / will give you a floating point number.

def intreverse(n):
    x=0
    d=0
    while n > 0:
        d = n % 10
        x= x * 10 + d
        n = n // 10
    return (x)

You can even improve you code by deleting the variable d before the while loop because its value is reassigned when you enter the loop, and you can also use the augmented assignment operator //= instead of n = n // 10, so you could would be:

def intreverse(n):
    x = 0

    while n > 0:
        d = n % 10
        x = x * 10 + d
        n //= 10

    return x

edited Feb 7, 2017 at 5:11

answered Feb 7, 2017 at 5:04

lmiguelvargasf

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1 Comment

lmiguelvargasf Over a year ago

@ArkaBhowmick, please validate the answer if it was useful, keep in mind that that is the way stackoverflow works

Steve Freed · Accepted Answer · 2019-10-12 00:47:07Z

0

If you are worried about overflow for a specific integer size you can check if the integer is within say a 32-bit range with a simple if statement [-2^(31), 2^(31) - 1]

def intreverse(self, x: int) -> int:
    negative = False
    if x < 0:
        negative = True
        x = x * -1

    res = 0
    while x != 0:
        res = (res * 10) + x % 10
        x = x // 10

        if (res > (2 ** 31) - 1) or (res < -(2 ** 31)):
            return 0

    return (res * -1) if negative else res

answered Oct 12, 2019 at 0:47

Steve Freed

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