递归列表理解 [英] Recursive list comprehension

问题描述

大家好。


我的列表看起来像[[''N''，''F'']，[''E'']，[' 'D'']]

我试着让它变平：[''N''，''F''，''E''，'D'']

如何通过列表理解来达到这样的效果？

两个周期完成了这项工作，但这种方式并不像pythonic ..

我试过

print [x for x in y in c_vars]

并得到NameError：name''y''未定义。


-

Timothy Babytch

解决方案

Timothy Babytch写道：
我的列表看起来像[[''N''，''F'']，[''E''] ，[''D'']]
我试着把它弄平：[''N''，''F''，''E''，'D'']

如何通过列表理解来达到这样的效果？
两个周期完成了这项工作，但那样做了方式看起来并不像pythonic ..

我试过打印[x for x in y in c_vars]
并得到NameError：name''y''未定义。

for表达式的顺序与嵌套循环的顺序相同：

items = [[''N''，''F'']，[''E'']，[''D'']]
[y for x中的y项目中的x]
[''N''，''F''，''E''，''D'']


我仍然会更喜欢for循环，因为它可以让你免于迭代
python中的子列表项：

data = []
for sub in [['' N''，''F'']，[''E'']，[''D'']]：
.... data.extend（sub）

....数据

[''N''，''F''，''E''，'D'']


彼得

Peter Otten写道：

for表达式的顺序与嵌套循环的顺序相同：

items = [[''N ''，''F'']，[''E'']，[''D'']]
[y代表x中y项目的x]

我仍然更喜欢for循环，因为它可以让你免于迭代在python中的子列表项：

data = []
for sub in [[''N''，''F'']，[''E'']，[''D'']]：

.. .data.extend（sub）
...

谢谢。这两个提示都很有帮助。


-

Timothy Babytch

2004年12月6日星期一09 ：26，Timothy Babytch写道：

大家好。

我的列表看起来像[[''N''，''F'']，[' 'E''，[''D'']]
我试着把它弄平：[''N'，''F''，''E''，'D'' ]

如何通过列表理解来实现这样的效果？
两个周期完成了这项工作，但那种方式看起来并不像pythonic ..

我试过
print [x for x in y for y in c_vars]
并得到NameError：name''y''未定义。

-
Timothy Babytch

我认为你用这样的发电机做到这一点：


def flatten（嵌套）：

表示嵌套子列表：

表示子列表中的元素：

yield element


n = [[''N''，''F'']，[''E''] ，[''D'']]

输出= []


for flatten（n）：

输出.append（价值）


打印输出


祝圣诞快乐


Peter Nuttall

Hi all.

I have a list that looks like [[''N'', ''F''], [''E''], [''D'']]
I try to make it flat one: [''N'', ''F'', ''E'', ''D'']

How can I archieve such an effect with list comprehension?
Two cycles did the job, but that way did not look pythonic..

I tried
print [x for x in y for y in c_vars]
and got NameError: name ''y'' is not defined.

--
Timothy Babytch

解决方案

Timothy Babytch wrote:

Hi all.

I have a list that looks like [[''N'', ''F''], [''E''], [''D'']]
I try to make it flat one: [''N'', ''F'', ''E'', ''D'']

How can I archieve such an effect with list comprehension?
Two cycles did the job, but that way did not look pythonic..

I tried
print [x for x in y for y in c_vars]
and got NameError: name ''y'' is not defined.

The order of the for expressions is as it would be for nested loops:

items = [[''N'', ''F''], [''E''], [''D'']]
[y for x in items for y in x] [''N'', ''F'', ''E'', ''D'']

I would still prefer a for loop because it spares you from iterating over
the sublist items in python:
data = []
for sub in [[''N'', ''F''], [''E''], [''D'']]: .... data.extend(sub)
.... data

[''N'', ''F'', ''E'', ''D'']

Peter

Peter Otten wrote:

The order of the for expressions is as it would be for nested loops:

items = [[''N'', ''F''], [''E''], [''D'']]
[y for x in items for y in x]

I would still prefer a for loop because it spares you from iterating over
the sublist items in python:

data = []
for sub in [[''N'', ''F''], [''E''], [''D'']]:

... data.extend(sub)
...

Thanks. Both tips were helpful.

--
Timothy Babytch

On Monday 06 Dec 2004 09:26, Timothy Babytch wrote:

Hi all.

I have a list that looks like [[''N'', ''F''], [''E''], [''D'']]
I try to make it flat one: [''N'', ''F'', ''E'', ''D'']

How can I archieve such an effect with list comprehension?
Two cycles did the job, but that way did not look pythonic..

I tried
print [x for x in y for y in c_vars]
and got NameError: name ''y'' is not defined.

--
Timothy Babytch

Hi,

I think you do it with a generator like this:

def flatten(nested):
for sublist in nested:
for element in sublist:
yield element

n=[[''N'', ''F''], [''E''], [''D'']]
output=[]

for value in flatten(n):
output.append(value)

print output

Have a merry Christmas

Peter Nuttall

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