Circularly shifting (or rotating) the digits the digits of a number in Python

Question

Suppose I have the following input:

How can I get the following output?

This is obtained by circularly shifting (or rotating) the digits of the input twice.

I have tried the following code:

number = 1234
bin(number >> 1)

but it is not producing the results I was expecting.

First of all you should probably save it as a string, not an integer — RnRoger, Sep 28 '18 at 12:31
"but i am getting 3412 as output". That's strange, on my machine that code prints 0b1001101001. I think the first thing you should do is look up the documentation for ">>" to confirm whether "right shifting" does what you think it does. — Kevin, Sep 28 '18 at 12:37
@Kevin i am trying to convert number into binary then right shift then binary into number — Tanya Chaudhary, Sep 28 '18 at 12:39

kalehmann · Accepted Answer · 2018-09-28T12:43:45.063

8

The >> operator does a binary bitshift.

It moves the binary representation of 1234 on place to the right, discarding the rightmost (least significant) bit.

Therefore you code does not result in 3412.

You probably want string rotation instead:

>>> def rotr(string, n):
...     return string[n:] + string[:n]
... 
>>> rotr("1234", 2)
'3412'

You can also convert it back to an integer afterwards

>>> int('3412')
3412

edited Sep 28 '18 at 12:43

answered Sep 28 '18 at 12:35

kalehmann

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thanks!! again like @onno the logic is simpler than what i thought to solve the problem – Tanya Chaudhary Sep 28 '18 at 12:47

score 3 · Answer 2 · answered Sep 28 '18 at 12:32

3

I would convert to string to be able to slice it.

number=1234
right_shift_no = 2
new_number = int(str(number)[right_shift_no:]+str(number)[:right_shift_no])

answered Sep 28 '18 at 12:32

onno

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thanku!! Logic of solving this problemof mine is complicated. thanks for sharing a easy logic – Tanya Chaudhary Sep 28 '18 at 12:44

score 3 · Answer 3 · answered Sep 28 '18 at 12:34

3

Here's the lazy man's version:

>>> from collections import deque
>>> number = 1234
>>> d = deque(str(number))
>>> d.rotate(2)
>>> result = int(''.join(d))
>>> result
3412

answered Sep 28 '18 at 12:34

timgeb

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joel · Answer 4 · 2018-09-28T13:12:28.910

2

If you must stick with numbers (though I'd go with the string option first)

from math import log10, floor
s = 2  # digits to shift by
p = 10 ** s  # that as a power of 10
n = 1234
rhs = n // p  # right hand side of result (here 12)
rhs_n = floor(log10(rhs)) + 1  # number of digits in rhs
rhs + (n % p) * 10 ** rhs_n  # add other digits, n % p, shifted by size of rhs

and all together in a function

from math import log10, floor

def rotate(n, s):
    p = 10 ** s
    rhs = n // p
    return rhs + (n % p) * 10 ** (floor(log10(rhs)) + 1)

edited Sep 28 '18 at 13:12

answered Sep 28 '18 at 12:37

joel

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hey thanks!!You need to explain me as its lil bit different from what i thought – Tanya Chaudhary Sep 28 '18 at 12:46
@TanyaChaudhary explained – joel Sep 28 '18 at 13:15

Circularly shifting (or rotating) the digits the digits of a number in Python

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