Question

我试图“压扁”一个数组，将其转换为1个单维项目集。我使用append命令，我得到了这个：

[['X', 'X'],['ff','ff','ff','ff','ff']]

但我希望将元素排序为：

['X','X','ff','ff','ff','ff','ff']

我不能使用string.join（）或string.split（）运算符。那么哪个是最明智的方式来执行此操作？

Answer 1

我认为你要找的是extend（）而不是append（）

>>> oldList = [['X', 'X'],['ff','ff','ff','ff','ff']]
>>> print oldList
[['X', 'X'], ['ff', 'ff', 'ff', 'ff', 'ff']]
>>> newList = []
>>> for item in oldList:
...     newList.extend( item )
>>> print newList
>>> ['X', 'X', 'ff', 'ff', 'ff', 'ff', 'ff']

Answer 2

使用列表理解：

alist = [['X', 'X'],['ff','ff','ff','ff','ff']]
print [j for i in alist for j in i ]

使用reduce：

reduce(lambda r,x:r+x, alist,[])

输出：

['X', 'X', 'ff', 'ff', 'ff', 'ff', 'ff']

Answer 3

使用itertools.chain或extend()

>>> from itertools import chain
>>> oldList = [['X', 'X'],['ff','ff','ff','ff','ff']]
>>> list(chain.from_iterable(oldList))
['X', 'X', 'ff', 'ff', 'ff', 'ff', 'ff']

>>> list1 = ['X', 'X']
>>> list1.extend(['ff','ff','ff','ff','ff'])
>>> list1
['X', 'X', 'ff', 'ff', 'ff', 'ff', 'ff']

Answer 4

为了完整起见，总有

In [1]: x = [['X', 'X'], ['ff', 'ff', 'ff', 'ff', 'ff']]
In [2]: sum(x, [])
Out[2]: ['X', 'X', 'ff', 'ff', 'ff', 'ff', 'ff']

但是

In [3]: [item for sublist in x for item in sublist]
Out[3]: ['X', 'X', 'ff', 'ff', 'ff', 'ff', 'ff']

应该更快，

In [4]: from itertools import chain
In [5]: list(chain.from_iterable(x))
Out[5]: ['X', 'X', 'ff', 'ff', 'ff', 'ff', 'ff']

应该是最快的。

在Python中使2D数组成为一维

4 个答案: