PYTHON

pivot index

# Time:  O(n)
# Space: O(1)

class Solution(object):
    def pivotIndex(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        total = sum(nums)
        left_sum = 0
        for i, num in enumerate(nums):
            if left_sum == (total-left_sum-num):
                return i
            left_sum += num
        return -1

pivot_table indexing

table = pd.pivot_table(df, values='D', index=['A', 'B'],
...                     columns=['C'], aggfunc=np.sum, fill_value=0)
>>> table
C        large  small
A   B
bar one      4      5
    two      7      6
foo one      4      1
    two      0      6