索引列表列表 [英] Indexing list of lists

问题描述

之前可能有人问过，但我找不到它。如果我有

a矩形列表列表，比如说，l = [[1,10]，[2,20]，[3,30]]，那么是

那里一个方便的语法，用于检索每个子列表的第i项？

我知道[i [0] for i in l]但是我希望有更多的东西

喜欢l [; 0]。


Hilde

This may have been asked before but I can''t find it. If I have
a rectangular list of lists, say, l = [[1,10],[2,20],[3,30]], is
there a handy syntax for retrieving the ith item of every sublist?
I know about [i[0] for i in l] but I was hoping for something more
like l[;0].

Hilde

推荐答案

嗨************* @ yahoo.de （Hilde Roth）写道：

hi*************@yahoo.de (Hilde Roth) writes:

这可能是之前被问过但我找不到。如果我有一个矩形列表列表，比如l = [[1,10]，[2,20]，[3,30]]，那么有一个方便的语法来检索第i个每个子列表中的项目？
我知道[i [0] for i in l]但是我希望有更多的东西像l [; 0]。

This may have been asked before but I can''t find it. If I have
a rectangular list of lists, say, l = [[1,10],[2,20],[3,30]], is
there a handy syntax for retrieving the ith item of every sublist?
I know about [i[0] for i in l] but I was hoping for something more
like l[;0].

如果你需要那么多东西，看看Numeric（或它的

替换，numarray），或者标准库的数组

模块。

John

If you need that kind of thing a lot, look at Numeric (or its
replacement, numarray), or perhaps the standard library''s array
module.
John

文章< 95 ***************** *********@posting.google.com>，
hi *************@yahoo.de （希尔德罗斯）写道：

In article <95**************************@posting.google.com >,
hi*************@yahoo.de (Hilde Roth) wrote:

这可能是之前被问到但我可以''找到它。如果我有一个矩形列表列表，比如l = [[1,10]，[2,20]，[3,30]]，那么有一个方便的语法来检索第i个每个子列表中的项目？
我知道[i [0] for i in l]但是我希望有更多的东西像l [; 0]。

This may have been asked before but I can''t find it. If I have
a rectangular list of lists, say, l = [[1,10],[2,20],[3,30]], is
there a handy syntax for retrieving the ith item of every sublist?
I know about [i[0] for i in l] but I was hoping for something more
like l[;0].

l = [[1,10]，[2,20]，[3,30]]
zip（* l）[0]

l = [[1,10],[2,20],[3,30]]
zip(*l)[0]

（1,2,3）


-

David Eppstein http://www.ics.uci.edu/ ~eppstein /

大学加州，欧文，信息学院和计算机科学

(1, 2, 3)

--
David Eppstein http://www.ics.uci.edu/~eppstein/
Univ. of California, Irvine, School of Information & Computer Science

Hilde Roth写道：

Hilde Roth wrote:

这可能是之前被问过但我找不到。如果我有一个矩形列表列表，比如l = [[1,10]，[2,20]，[3,30]]，那么有一个方便的语法来检索第i个每个子列表中的项目？
我知道[i [0] for i in l]但是我希望有更多的东西像l [; 0]。

This may have been asked before but I can''t find it. If I have
a rectangular list of lists, say, l = [[1,10],[2,20],[3,30]], is
there a handy syntax for retrieving the ith item of every sublist?
I know about [i[0] for i in l] but I was hoping for something more
like l[;0].

如果效率不是问题和/或你需要

[列表中项目的[项目[索引]]一次多个索引，你可以

do：

If efficiency is not an issue and/or you need
[item[index] for item in theList] for more than one index at a time, you can
do:

s = [[1,2]，[3,4]]
t = zip（* s）
t
[（1,3），（2,4）] t [1]
（2,4）

s = [[1,2],[3,4]]
t = zip(*s)
t [(1, 3), (2, 4)] t[1] (2, 4)

这会创建矩阵的转置（？）副本。如果您只需要

对条目的读取权限，那么创建tupples而不是内部列表的副作用应该没有坏处。


Peter

This creates a transposed (?) copy of the "matrix". The side effect of
creating tupples instead of inner lists should do no harm if you need only
read access to the entries.

Peter

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