Create power-set (the set of all possible subsets) from a python list

powerset.py

def power_set(orignal_list):
    ''' 
    PowerSet of a List
    
    @param orignal_list: list from which to construct a powerset
    '''
    list_size = len(orignal_list)
    num_sets = 2**list_size
    powerset = []
    # Don't include empty set
    for i in range(num_sets)[1:]:
        subset = []
        binary_digits = list(int2bin(i,list_size))
        list_indices = range(list_size)
        for (bit,index) in zip(binary_digits,list_indices):
            if bit == '1':
                subset.append(orignal_list[index])
        powerset.append(subset)
    return powerset


def int2bin(n, count=24):
    """returns the binary of integer n, using count number of digits"""
    return "".join([str((n >> y) & 1) for y in range(count-1, -1, -1)])