Elias Gamma Encoding in Python

The Elias gamma code is a universal code that is used to encode a sequence of positive integers. It is developed by Peter Elias. It is most useful when the upper-bound of integers cannot be determined beforehand.

Steps in Encoding:

To encode a number X,

Find the largest N, with
$2^{N}\leq X$ (greater power of 2).
Encode N using Unary coding(i.e N zeroes followed by a one).
Append the integer $(X-2^{N})$ using N digits in Binary.

Example: Let’s consider an example whwre we want to encode 10,
We can represent 10 as:
$10=2^{3} + 2$ .
Step1: Here, largest N = 3
Step2: N(=3) in Unary followed by a one = 0001
Step3: Now Representation of 2 in Binary using N(=3) digits = 010
So, Elias gamma encoding of 10 = 0001010

Below is the implementation of the above approach.

# Python3 implementation 
from math import log 
  
log2 = lambda x: log(x, 2) 
  
def Unary(x): 
    return (x-1)*'0'+'1'
  
def Binary(x, l = 1): 
    s = '{0:0%db}' % l 
    return s.format(x) 
      
def Elias_Gamma(x): 
    if(x == 0):  
        return '0'
  
    n = 1 + int(log2(x)) 
    b = x - 2**(int(log2(x))) 
  
    l = int(log2(x)) 
  
    return Unary(n) + Binary(b, l) 
      
print(Elias_Gamma(10)) 

Output:

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