python的reduce函数

python的reduce函数

官方说明：

def reduce(function, sequence, initial=None): # real signature unknown; restored from __doc__
    """
    reduce(function, sequence[, initial]) -> value
    
    Apply a function of two arguments cumulatively to the items of a sequence,
    from left to right, so as to reduce the sequence to a single value.
    For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates
    ((((1+2)+3)+4)+5).  If initial is present, it is placed before the items
    of the sequence in the calculation, and serves as a default when the
    sequence is empty.
    """
    pass

function是一个二元函数，随后的参数可以进行累加的，如图

尝试举例：

max1  = [
    [[0,1],
     [1,2],
     [1,1]],
    [[2,3],
     [3,4],
     [3,3]]
    ]

ten = reduce(np.add,max1)
print ten
输出结果：
[[2 4]
 [4 6]
 [4 4]]

显然可以看出来，reduce是用来降低维度的，从2×3×2三维变成3*2二维的矩阵，对应位置上的元素相加的