int.bit_length()

bit_length.py

n = int(1e6)

def f(x):
  l = 0
  while x != 0:
    l += 1
    x >>= 1
  return l
f(n) # 20

import math
math.floor(math.log2(n)) + 1 # 20

len(bin(n)[2:]) # 20

n.bit_length() # 20

c.c

#include <limits.h>
#include <stdio.h>
unsigned int f(unsigned int x) {
  return CHAR_BIT * sizeof(int) - __builtin_clz(x);
}
int main(void) {
  printf("[+] %d\n", f(1e6));
  return 0;
}