Max sum of contiguous subarray

maxSubArray.py

#based on idea that none of the prefixes of
#maximal sum array can be negative(interesting, isn't it)
def maxSubArray(self, A):
        cursum = 0
        maxsum = -999999999999
        for item in A:
            cursum += item
            maxsum = max(cursum, maxsum)
            if cursum < 0:
                cursum = 0
        return maxsum