Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #30968 > unrolled thread

Insert item before each element of a list

Back to article view | Back to comp.lang.python

Contents

  Insert item before each element of a list mooremathewl@gmail.com - 2012-10-08 12:28 -0700
    Re: Insert item before each element of a list Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-08 13:42 -0600
    Re: Insert item before each element of a list MRAB <python@mrabarnett.plus.com> - 2012-10-08 20:43 +0100
    Re: Insert item before each element of a list Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-08 14:04 -0600
    Re: Insert item before each element of a list Agon Hajdari <agonh@freenet.de> - 2012-10-08 22:12 +0200
    Re: Insert item before each element of a list Peter Otten <__peter__@web.de> - 2012-10-08 23:12 +0200
    RE: Insert item before each element of a list "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-10-08 21:15 +0000
    Re: Insert item before each element of a list Agon Hajdari <agonh@freenet.de> - 2012-10-08 23:39 +0200
    RE: Insert item before each element of a list "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-10-08 22:12 +0000
    Re: Insert item before each element of a list Paul Rubin <no.email@nospam.invalid> - 2012-10-08 15:24 -0700
    Re: Insert item before each element of a list Nobody <nobody@nowhere.com> - 2012-10-08 23:35 +0100
    Re: Insert item before each element of a list "Alex" <foo@email.invalid> - 2012-10-09 00:08 +0000
    Re: Insert item before each element of a list Terry Reedy <tjreedy@udel.edu> - 2012-10-08 21:58 -0400
      Re: Insert item before each element of a list Roy Smith <roy@panix.com> - 2012-10-08 22:06 -0400
        Re: Insert item before each element of a list rusi <rustompmody@gmail.com> - 2012-10-08 19:34 -0700
          Re: Insert item before each element of a list rusi <rustompmody@gmail.com> - 2012-10-08 19:39 -0700
            Re: Insert item before each element of a list Hans Mulder <hansmu@xs4all.nl> - 2012-10-12 00:21 +0200
              Re: Insert item before each element of a list Terry Reedy <tjreedy@udel.edu> - 2012-10-11 19:38 -0400
              Re: Insert item before each element of a list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-12 02:16 +0000
          Re: Insert item before each element of a list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-09 12:01 +0000
        Re: Insert item before each element of a list alex23 <wuwei23@gmail.com> - 2012-10-08 20:11 -0700
        Re: Insert item before each element of a list mooremathewl@gmail.com - 2012-10-09 07:03 -0700
    Re: Insert item before each element of a list Duncan Booth <duncan.booth@invalid.invalid> - 2012-10-09 11:40 +0000
      Re: Insert item before each element of a list Peter Otten <__peter__@web.de> - 2012-10-09 14:55 +0200

Page 2 of 2 — ← Prev page 1 [2]

#30988

On Oct 9, 12:06 pm, Roy Smith <r...@panix.com> wrote:
> I'm going to go with this one.  I think people tend to over-abuse list
> comprehensions.

I weep whenever I find `_ = [...]` in other people's code.

[toc] | [prev] | [next] | [standalone]

#31022

On Monday, October 8, 2012 10:06:50 PM UTC-4, Roy Smith wrote:
> In article <mailman.1976.1349747963.27098.python-list@python.org>,
> 

(big snip)

> 
> 
> > y = list(itertools.chain.from_iterable(('insertme', x[i]) for i in range(len(x))))
> 
> 
> 
> A statement ending in four close parens is usually going to be pretty 
> 
> difficult to figure out.  This is one where I had to pull out my pencil 
> 
> and start pairing them off manually to figure out how to parse it.


Fair enough.  I admit I was looking for a tricky one-liner, which rarely leads to good code...I should know better.

Thanks for all the feedback from everyone.  It's amazing how much Python one can learn just asking about a small section of code!

[toc] | [prev] | [next] | [standalone]

#31006

mooremathewl@gmail.com wrote:

> What's the best way to accomplish this?  Am I over-complicating it? 
> My gut feeling is there is a better way than the following: 
> 
>>>> import itertools
>>>> x = [1, 2, 3]
>>>> y = list(itertools.chain.from_iterable(('insertme', x[i]) for i in
>>>> range(len(x)))) y
> ['insertme', 1, 'insertme', 2, 'insertme', 3]
> 
> I appreciate any and all feedback.
> 

Given the myriad of proposed solutions, I'm surprised nobody has suggested 
good old list slicing:

>>> x = [1,2,3]
>>> y = ['insertme']*(2*len(x))
>>> y[1::2] = x
>>> y
['insertme', 1, 'insertme', 2, 'insertme', 3]

-- 
Duncan Booth

[toc] | [prev] | [next] | [standalone]

#31013

Duncan Booth wrote:

> mooremathewl@gmail.com wrote:
> 
>> What's the best way to accomplish this?  Am I over-complicating it?
>> My gut feeling is there is a better way than the following:
>> 
>>>>> import itertools
>>>>> x = [1, 2, 3]
>>>>> y = list(itertools.chain.from_iterable(('insertme', x[i]) for i in
>>>>> range(len(x)))) y
>> ['insertme', 1, 'insertme', 2, 'insertme', 3]
>> 
>> I appreciate any and all feedback.
>> 
> 
> Given the myriad of proposed solutions, I'm surprised nobody has suggested
> good old list slicing:

My post on gmane 

http://thread.gmane.org/gmane.comp.python.general/718940/focus=718947

apparently didn't make it through to the list.

>>>> x = [1,2,3]
>>>> y = ['insertme']*(2*len(x))
>>>> y[1::2] = x
>>>> y
> ['insertme', 1, 'insertme', 2, 'insertme', 3]

An advantage of this approach -- it is usually much faster.

[toc] | [prev] | [standalone]

Page 2 of 2 — ← Prev page 1 [2]

Back to top | Article view | comp.lang.python

csiph-web