Find an index in an array such that its prefix sum equals its suffix sum.

Equi.py

def solution(A):
    # write your code in Python 2.7
    s = []
    tmp = 0
    n = len(A)
    for a in A:
        tmp = a +  tmp
        s.append(tmp)
    s.append(0)

    for i in xrange(0,n):
        if s[i-1] == s[n-1]-s[i]:
            return i
    return -1