python-How to reverse an negative integer or non-integer

Question

I am learning python and I meet some troubles.

I want to write the script to reverse a negative integer ” -1234 to 4321- ” and non-integer ” 1.234 to 432.1″. please help me.
P.S. cannot use “str()” function

I just only can write the script to reverse positive integer 1234 to 4321

def reverse_int(n):

    x = 0
    while n > 0:
        x *= 10
        x += n % 10
        n /= 10
    return x
print reverse_int(1234)

Asked By: GregMaddux

||

Source

Answer 1

Use this as a guide and make it work for floating point values as well:

import math

def reverse_int(n):
    if abs(n) < 10:
        v = chr(abs(n) + ord('0'))
        if n < 0: v += '-'
        return v
    else:
        x = abs(n) % 10
        if n < 0: return chr(x + ord('0')) + reverse_int(math.ceil(n / 10))
        else: return chr(x + ord('0')) + reverse_int(math.floor(n / 10))

print reverse_int(1234)

Answered By: smac89

Answer 2

how about using your code, but just concatenate a - when n is negative?

rev_int.py:

def reverse_int(m):
    x = 0
    n = m
    if m < 0 :
      n *= -1
    while n > 0 :
        x *= 10
        x += n % 10
        n /= 10
    if m < 0:
      #concatenate a - sign at the end
      return `x` + "-"
    return x

print reverse_int(1234)
print reverse_int(-1234)

This produces:

$ python rev_int.py
4321
4321-

Answered By: Curious

Answer 3

Why not just do the following?:

def reverse(num):
    revNum = ''
    for i in `num`:
        revNum = i + revNum
    return revNum

print reverse(1.12345)
print reverse(-12345)

These would print 54321.1 and 54321-.

Answered By: Aaron

Answer 4

Using SLICING EASILY DONE IT

def uuu(num):
if num >= 0: 
    return int(str(num)[::-1])
else:
    return int('-{val}'.format(val = str(num)[1:][::-1]))

Answered By: Sunil Chaudhary

Answer 5

def reve(x):
    x=str(x)
    if x[0]=='-':
        a=x[::-1]
        return f"{x[0]}{a[:-1]}"
    else:
        return x[::-1]

print(reve("abc"))
print(reve(123))
print(reve(-123))

#output
cba
321
-321

Answered By: Mukund Biradar

Answer 6

Below code runs fine on Python-3 and handles positive and negative integer case. Below code takes STDIN and prints the output on STDOUT.

Note: below code handles only the integer case and doesn’t handles the
non-integer case.

def reverseNumber(number):
        x = 0
        #Taking absolute of number for reversion logic
        n = abs(number)
        rev = 0
        #Below logic is to reverse the integer
        while(n > 0):
            a = n % 10
            rev = rev * 10 + a
            n = n // 10
        #Below case handles negative integer case
        if(number < 0):
            return (str(rev) + "-")
        return (rev)
#Takes STDIN input from the user
number=int(input())
#Calls the reverseNumber function and prints the output to STDOUT
print(reverseNumber(number))

Answered By: Ankit Raj

Answer 7

Using str convert method.

num = 123
print(str(num)[::-1])

Answered By: Mahesh Chougule

python-How to reverse an negative integer or non-integer

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