[Tutor] Reversing digits of number (WAS Re: (no subject))

[Prahlad Vaidyanathan]

Hi,

On Fri, 09 Aug 2002 Anand Ramakrishna spewed into the ether:
> Hi,
>     I am having a strange problem with my python code for
>     reversing a number. I tried it on a few combinations and
>     works fine with most of them except when the number starts
>     in '1'. If I give input as 123 it reverses and displays as
>     442. If I give input as 12 it reverses and displays as 12.

    Well, your logic is a *little* flawed. Read below ..

[-- snippity --]
> print 'This program accepts a number and then reverses it'
> number = int(raw_input("Enter a number = "))
> temp_var = 0
>  
> while (number/10) > 1 :
                   ^^^^

    Here is your problem. This should be ">= 1". For example,
when you enter "12", look at what happens.

"""
>>> number = 12
>>> number/10
1
>>> (number/10) > 1 ## False
0
>>> (number/10) >= 1 ## True
1
>>>
"""

    Therefore, by your method, if the 1st digit is exactly "1",
then the program comes out of the while loop, and thus the
"number" now holds the 1st *and* the 2nd digit (12, in this case)
when it enters the else loop.

    Thus, you get results like so :

        Input: 123  => Output: ((3*10) + 12) = 42
        Input: 1557 => Output: ((75*10) + 15) = 765

    HTH,

pv.
-- 
Prahlad Vaidyanathan  <http://www.symonds.net/~prahladv/>

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