Algorithms/Find maximum/Python method 2

def findMax(a):
 
    length = len(a)
 
    if length == 0 :
        return 0
 
    elif length == 1 :
        return a[0]
 
    elif length == 2 :
 
        if a[0] > a[1] :
            return a[0] 
        else :
            return a[1]
 
    half = length / 2
 
    list_A = a[:half]
    list_B = a[half:]
 
    max_A = findMax(list_A)
    max_B = findMax(list_B)
 
    if max_A > max_B :
        return max_A
    else :
        return max_B