Python Binary Summation

Question

While looking at some SageMath code I came across the following snippet:

bits = n - sum(n.digits(2))

Since I had no idea what digitsdid I went ahead to attempt it with a value of n = 5:

n = 5
print(n.digits(2))
[1, 0, 1]

And if I run the complete line the result is (rather obviously)

n = 5
print(sum(n.digits(2)))
2

How could I achieve this in pure python? Conversion to strings and back are dead slow, so I'd like to avoid those. Is there a fast solution to this?

The sum of all the individual bits of a number (therefore the number of 1's in a number's bit representation). *e.g:* 5 -> 101 -> 1+0+1 -> 2 — Bernardo Meurer, Jan 05 '16 at 15:35

FunkySayu · Answer 1 · 2016-01-05T15:36:45.237

2

If you are looking to the number of non-zero bits :

bin(5).count("1")

edited Jan 05 '16 at 15:36

answered Jan 05 '16 at 15:35

FunkySayu

I think it will perform even better if you remove `[2:]` which creates a new list. – Delgan Jan 05 '16 at 15:36

1 Answers1