write a function to get the sum of base n numbers in base n in python

Question

I want to write a function that gets base and some numbers that are in base n as its input and returns sum of the args in base n. I thought I first get the first digit of the numbers and calculate the sum and then the other digit and so on... but the thing is I can't get the second digit and my code just adds the first digit: (n between 2 and 10)

def sum_base(base, *args):
tot = 0
s = "" 

for num in args:
    rem = num % base
    tot += rem
if tot >= base:
    tot = tot % base
    carry = tot // base
s += str(tot)    

num = num // 10

return s


print(sum_base(2, 1111,1111,11111,10111))

could anyone help me modify the code? Thanks

So you want a function which will calculate sum for any base passed? — Bhagyesh Dudhediya, Sep 03 '21 at 12:43
what is the maximum base ? is it base 10 ? if not, you should use string instead — patate1684, Sep 03 '21 at 12:57
Does this answer your question? [Adding numbers with bases](https://stackoverflow.com/questions/22446884/adding-numbers-with-bases) — Ironkey, Sep 03 '21 at 12:58
Consider an appoach that decodes your input values to integers. sum it. then encode it back to the correct base. — Jason Chia, Sep 03 '21 at 13:01
Don't use an `int` to represent a number in a different base, it's just causing confusion. Use a string instead, makes it simpler and also works for bases > 10. — tobias_k, Sep 03 '21 at 13:03
@Ironkey yes my question is similar but the question you mentioned doesn't have helpful answers — Yasaman Shokri, Sep 03 '21 at 13:05
theres also [this](https://stackoverflow.com/questions/2267362/how-to-convert-an-integer-to-a-string-in-any-base) — Ironkey, Sep 03 '21 at 13:05
@JasonChia I thought that way but I think that is not efficient — Yasaman Shokri, Sep 03 '21 at 13:10
@Yasaman Shokri Were you looking for an optimal method? Are you limited by time/space? — Jason Chia, Sep 03 '21 at 13:20

3dSpatialUser · Answer 1 · 2021-09-03T13:04:37.497

I am not sure if this helps, since it is not entirely clear to me what you want to do.

But if you want to add numbers this is what I would do:

Convert number to integer with given base:

int(str(number), base)

This returns an integer with base 10. The base has to be a number and number should be a string (or one can convert it to string using str()).

Then I would add all numbers in your arguments, or sum the whole list.

Thereafter one can use numpy to convert back to a string with a given base: https://numpy.org/doc/stable/reference/generated/numpy.base_repr.html.

import numpy as np
np.base_repr(sum, base=base)

The example:

def sum_base(base, *args):
    l = [int(str(num), base) for num in args]
    return np.base_repr(sum(l), base=base)

sum_base(2, 111, 111, 111)
'10101'

binary 111 is 7 with base 10, three times 7 is 21 (in base 10) which equal 1* 1 + 1* 4 + 1* 16 in binary (10101).

patate1684 · Accepted Answer · 2021-09-03T13:43:53.823

you can do this if you want a solution without library:

def sum_base(base, *args):
    def numberToBase(n, b):
        if n == 0:
            return [0]
        digits = []
        while n:
            digits.append(int(n % b))
            n //= b
        # at this point, digits[::-1] is the list of digits of n at base b
        return int(''.join(map(str, digits[::-1]))) # convert a list of digits into a int
        
    # first, convert all number to base 10 and take the sum
    sum_base10 = sum([int(str(number), base) for number in args])
    
    # second, convert the base10 sum into base b with the function numberToBase define above
    return numberToBase(sum_base10, base)


print(sum_base(2, 1111,1111,11111,10111)) # binary
print(sum_base(10, 10,12,6,3))            # decimal
print(sum_base(8, 325, 471))              # octal

output:

1010100
31
1016

write a function to get the sum of base n numbers in base n in python

2 Answers2