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Howto flaten a list of lists was (Explanation of this Python language feature)

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  Howto flaten a list of lists was (Explanation of this Python language feature) Mark H Harris <harrismh777@gmail.com> - 2014-03-28 16:56 -0500
    Re: Howto flaten a list of lists was (Explanation of this Python language feature) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-28 22:12 +0000
      Re: Howto flaten a list of lists was (Explanation of this Python language feature) Mark H Harris <harrismh777@gmail.com> - 2014-03-28 17:23 -0500
        Re: Howto flaten a list of lists was (Explanation of this Python language feature) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-29 02:33 +0000
          Re: Howto flaten a list of lists was (Explanation of this Python language feature) Mark H Harris <harrismh777@gmail.com> - 2014-03-28 22:04 -0500
            Re: Howto flaten a list of lists was (Explanation of this Python language feature) Rustom Mody <rustompmody@gmail.com> - 2014-03-28 20:21 -0700
              Re: Howto flaten a list of lists was (Explanation of this Python language feature) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-29 15:46 +0000
            Re: Howto flaten a list of lists was (Explanation of this Python language feature) Chris Angelico <rosuav@gmail.com> - 2014-03-29 14:21 +1100
              Re: Howto flaten a list of lists was (Explanation of this Python language feature) Mark H Harris <harrismh777@gmail.com> - 2014-03-28 22:39 -0500
      Re: Howto flaten a list of lists was (Explanation of this Python language feature) Mark H Harris <harrismh777@gmail.com> - 2014-03-28 17:23 -0500
      Re: Howto flaten a list of lists was (Explanation of this Python language feature) mm0fmf <none@mailinator.com> - 2014-03-29 15:59 +0000

#69285 — Howto flaten a list of lists was (Explanation of this Python language feature)

On Fri, Mar 21, 2014 at 1:42 PM, vasudevram <vasudevram@gmail.com> wrote:
 >> Can anyone - maybe one of the Python language core team, or someone 
 >> with knowledge of the internals of Python - can explain why this 
 >> code works, and whether the different occurrences of the name x in 
 >> the expression, are in different scopes or not? :
 >>
 >> x = [[1,2], [3,4], [5,6]]
 >>     [x for x in x for x in x]

 > I'll give this +1 for playfulness, and -2 for lack of clarity.

 > I hope no one thinks this sort of thing is good to do in real-life code.

No. This has to be a better way to flatten lists:

 >>> from functools import reduce

 >>> import operator as λ

 >>> reduce(λ.add, l)
[1, 2, 3, 4, 5, 6, 7, 8, 9]

 >>>


marcus

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#69290

On 28/03/2014 21:56, Mark H Harris wrote:
> On Fri, Mar 21, 2014 at 1:42 PM, vasudevram <vasudevram@gmail.com> wrote:
>  >> Can anyone - maybe one of the Python language core team, or someone
>  >> with knowledge of the internals of Python - can explain why this >>
> code works, and whether the different occurrences of the name x in >>
> the expression, are in different scopes or not? :
>  >>
>  >> x = [[1,2], [3,4], [5,6]]
>  >>     [x for x in x for x in x]
>
>  > I'll give this +1 for playfulness, and -2 for lack of clarity.
>
>  > I hope no one thinks this sort of thing is good to do in real-life code.

Strange, I thought Dan Stromberg wrote the above.
>
> No. This has to be a better way to flatten lists:
>
>  >>> from functools import reduce
>
>  >>> import operator as λ
>
>  >>> reduce(λ.add, l)
> [1, 2, 3, 4, 5, 6, 7, 8, 9]
>

Why reinvent yet another way of flattening lists, particulary one that 
doesn't use the far more sensible:-

from operator import add

As for the stupid symbol that you're using, real programmers don't give 
a damn about such things, they prefer writing plain, simple, boring code 
that is easy to read.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence

---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com

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#69291

On 3/28/14 5:12 PM, Mark Lawrence wrote:
>>
>> No. This has to be a better way to flatten lists:
>>
>>  >>> from functools import reduce
>>
>>  >>> import operator as λ
>>
>>  >>> reduce(λ.add, l)
>> [1, 2, 3, 4, 5, 6, 7, 8, 9]
>>
>
> Why reinvent yet another way of flattening lists, particulary one that
> doesn't use the far more sensible:-

    { particularly }

>
> from operator import add
>
> As for the stupid symbol that you're using, real programmers don't give
> a damn about such things, they prefer writing plain, simple, boring code
> that is easy to read.

:-))    as RMS would say, "playful hacking, dude, playful hacking..."

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#69294

Mark, please stop posting to the newsgroup comp.lang.python AND the 
mailing list python-list@python.org. They mirror each other. Your posts 
are not so important that we need to see everything twice.


-- 
Steven D'Aprano
http://import-that.dreamwidth.org/

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#69296

On 3/28/14 9:33 PM, Steven D'Aprano wrote:
> Mark, please stop posting to the newsgroup comp.lang.python AND the
> mailing list python-list@python.org. They mirror each other. Your posts
> are not so important that we need to see everything twice.

Its not my fault, Steven. Something goofy is going on. My address says 
only comp.lang.python

I have no idea why some of these messages are being duplicated on the 
mailing list. I only post to the news group.

Anyways, sorry.  I'll keep checking this.

regards,

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#69299

On Saturday, March 29, 2014 8:34:19 AM UTC+5:30, Mark H. Harris wrote:
> On 3/28/14 9:33 PM, Steven D'Aprano wrote:
> > Mark, please stop posting to the newsgroup comp.lang.python AND the
> > mailing list (...). They mirror each other. Your posts
> > are not so important that we need to see everything twice.

> Its not my fault, Steven. Something goofy is going on. My address says 
> only comp.lang.python

> I have no idea why some of these messages are being duplicated on the 
> mailing list. I only post to the news group.

> Anyways, sorry.  I'll keep checking this.

> regards,

Just use the amazing, fool-safe, fail-proof google-groups.
And enjoy bliss.

[Uh... And now I need to run... Out of sprinting practice...]

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#69330

On 29/03/2014 03:21, Rustom Mody wrote:
> On Saturday, March 29, 2014 8:34:19 AM UTC+5:30, Mark H. Harris wrote:
>> On 3/28/14 9:33 PM, Steven D'Aprano wrote:
>>> Mark, please stop posting to the newsgroup comp.lang.python AND the
>>> mailing list (...). They mirror each other. Your posts
>>> are not so important that we need to see everything twice.
>
>> Its not my fault, Steven. Something goofy is going on. My address says
>> only comp.lang.python
>
>> I have no idea why some of these messages are being duplicated on the
>> mailing list. I only post to the news group.
>
>> Anyways, sorry.  I'll keep checking this.
>
>> regards,
>
> Just use the amazing, fool-safe, fail-proof google-groups.
> And enjoy bliss.
>
> [Uh... And now I need to run... Out of sprinting practice...]
>

Blast, you beat me to it, and I never could sprint :)

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence

---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com

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#69300

On Sat, Mar 29, 2014 at 2:04 PM, Mark H Harris <harrismh777@gmail.com> wrote:
> Its not my fault, Steven. Something goofy is going on. My address says only
> comp.lang.python

Well, something's causing your messages to come out multiple times and
with different subject lines :)

ChrisA

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#69302

On 3/28/14 10:21 PM, Chris Angelico wrote:
> Well, something's causing your messages to come out multiple times and
> with different subject lines :)

    I changed the subject line ( which I did twice because the first 
post said it had an error and did not post; which apparently was a lie).

    Then I posted again (this time it went without error, but came back 
duplicated.  In any case ONLY the news group was in the to: field. Very 
strange. All of this crap started happening a couple of days back when 
Thunderbird updated their client (I should know better than to accept that).

Anyway, things were supposed to be better once I switched from gg.  uh, huh.

Well, at least the line wrapping thing is fixed.

marcus

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#69292

On 3/28/14 5:12 PM, Mark Lawrence wrote:
>>
>> No. This has to be a better way to flatten lists:
>>
>>  >>> from functools import reduce
>>
>>  >>> import operator as λ
>>
>>  >>> reduce(λ.add, l)
>> [1, 2, 3, 4, 5, 6, 7, 8, 9]
>>
>
> Why reinvent yet another way of flattening lists, particulary one that
> doesn't use the far more sensible:-

    { particularly }

>
> from operator import add
>
> As for the stupid symbol that you're using, real programmers don't give
> a damn about such things, they prefer writing plain, simple, boring code
> that is easy to read.

:-))    as RMS would say, "playful hacking, dude, playful hacking..."

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#69331

On 28/03/2014 22:12, Mark Lawrence wrote:
> As for the stupid symbol that you're using, real programmers don't give
> a damn about such things, they prefer writing plain, simple, boring code
> that is easy to read

What he said.

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