python中flatten()函数用法详解

>>> a = [[1,3],[2,4],[3,5]]
>>> a = array(a)
>>> a.flatten()
array([1, 3, 2, 4, 3, 5])

>>> a = [[1,3],[2,4],[3,5]]
>>> a = mat(a)
>>> y = a.flatten()
>>> y
matrix([[1, 3, 2, 4, 3, 5]])    ## 经过降维仍为矩阵类型
>>> y = a.flatten().A
>>> y
array([[1, 3, 2, 4, 3, 5]])        ## 此时变为数组类型
>>> shape(y)
(1, 6)
>>> shape(y[0])
(6,)
>>> y = a.flatten().A[0]
>>> y
array([1, 3, 2, 4, 3, 5])

>>> a = [[1,3],[2,4],["abc","def"]]
>>> a.flatten()

# 报错
Traceback (most recent call last):
 File "<pyshell#10>", line 1, in <module>
  a.flatten()
AttributeError: 'list' object has no attribute 'flatten'

>>> a = [[1,3],[2,4],["abc","def"]]
>>> a1 = [y for x in a for y in x]
>>> a1
[1, 3, 2, 4, 'abc', 'def']