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Conversion of List of Tuples

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  Conversion of List of Tuples subhabangalore@gmail.com - 2012-12-03 11:58 -0800
    Re: Conversion of List of Tuples John Gordon <gordon@panix.com> - 2012-12-03 20:04 +0000
      Re: Conversion of List of Tuples MRAB <python@mrabarnett.plus.com> - 2012-12-03 20:13 +0000
      Re: Conversion of List of Tuples Chris Angelico <rosuav@gmail.com> - 2012-12-04 07:17 +1100
    Re: Conversion of List of Tuples Chris Kaynor <ckaynor@zindagigames.com> - 2012-12-03 12:10 -0800
    Re: Conversion of List of Tuples subhabangalore@gmail.com - 2012-12-03 13:14 -0800
      Re: Conversion of List of Tuples John Gordon <gordon@panix.com> - 2012-12-03 22:02 +0000
      Re: Conversion of List of Tuples Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-12-03 22:11 +0000
        Re: Conversion of List of Tuples Walter Hurry <walterhurry@lavabit.com> - 2012-12-03 22:43 +0000
    Re: Conversion of List of Tuples Gary Herron <gherron@digipen.edu> - 2012-12-03 12:08 -0800
    Re: Conversion of List of Tuples Alexander Blinne <news@blinne.net> - 2012-12-04 10:44 +0100
      Re: Conversion of List of Tuples Hans Mulder <hansmu@xs4all.nl> - 2012-12-04 12:45 +0100
        Re: Conversion of List of Tuples Neil Cerutti <neilc@norwich.edu> - 2012-12-04 13:54 +0000

#34184 — Conversion of List of Tuples

Dear Group,

I have a tuple of list as,

tup_list=[(1,2), (3,4)]
Now if I want to covert as a simple list,

list=[1,2,3,4]

how may I do that?

If any one can kindly suggest? Googling didn't help much.

Regards,
Subhabrata. 

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#34185

In <6049bc85-6f8e-429b-a855-ecef47a9d28e@googlegroups.com> subhabangalore@gmail.com writes:

> Dear Group,

> I have a tuple of list as,

> tup_list=[(1,2), (3,4)]
> Now if I want to covert as a simple list,

> list=[1,2,3,4]

> how may I do that?

new_list = []

for t in tup_list:
    for item in t:
        new_list.append(item)

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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#34187

On 2012-12-03 20:04, John Gordon wrote:
> In <6049bc85-6f8e-429b-a855-ecef47a9d28e@googlegroups.com> subhabangalore@gmail.com writes:
>
>> Dear Group,
>
>> I have a tuple of list as,
>
>> tup_list=[(1,2), (3,4)]
>> Now if I want to covert as a simple list,
>
>> list=[1,2,3,4]
>
>> how may I do that?
>
> new_list = []
>
> for t in tup_list:
>      for item in t:
>          new_list.append(item)
>
Or you could use .extend:

new_list = []

for t in tup_list:
     new_list.extend(t)

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#34188

On Tue, Dec 4, 2012 at 7:04 AM, John Gordon <gordon@panix.com> wrote:
> In <6049bc85-6f8e-429b-a855-ecef47a9d28e@googlegroups.com> subhabangalore@gmail.com writes:
>
>> Dear Group,
>
>> I have a tuple of list as,
>
>> tup_list=[(1,2), (3,4)]
>> Now if I want to covert as a simple list,
>
>> list=[1,2,3,4]
>
>> how may I do that?
>
> new_list = []
>
> for t in tup_list:
>     for item in t:
>         new_list.append(item)

Which can be written more succintly as:

new_list = []
for t in tup_list:
    new_list.extend(t)

In more general terms, what you're looking to do here is *flatten*
your structure. Not sure if that would have helped in the web search
that you doubtless did before asking this question. :)

ChrisA

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#34186

On Mon, Dec 3, 2012 at 11:58 AM,  <subhabangalore@gmail.com> wrote:
> Dear Group,
>
> I have a tuple of list as,
>
> tup_list=[(1,2), (3,4)]
> Now if I want to covert as a simple list,
>
> list=[1,2,3,4]
>
> how may I do that?
>
> If any one can kindly suggest? Googling didn't help much.

If you know they are always exactly two levels deep, you can use
nested loops (in comprehension form):
[item for tuple_ in list_ for item in tuple_]

That could also be written how John recommended, in three lines.

>
> Regards,
> Subhabrata.
> --
> http://mail.python.org/mailman/listinfo/python-list

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#34191

On Tuesday, December 4, 2012 1:28:17 AM UTC+5:30, subhaba...@gmail.com wrote:
> Dear Group,
> 
> 
> 
> I have a tuple of list as,
> 
> 
> 
> tup_list=[(1,2), (3,4)]
> 
> Now if I want to covert as a simple list,
> 
> 
> 
> list=[1,2,3,4]
> 
> 
> 
> how may I do that?
> 
> 
> 
> If any one can kindly suggest? Googling didn't help much.
> 
> 
> 
> Regards,
> 
> Subhabrata.

Thanks. But I am not getting the counter "5posts 0 views"...if moderator can please check the issue.

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#34193

In <e89cddcc-71ab-4223-b66e-8c853634aa8f@googlegroups.com> subhabangalore@gmail.com writes:

> Thanks. But I am not getting the counter "5posts 0 views"...if
> moderator can please check the issue.

I logged in via Google Groups and all the replies were present.  What
is your question?

(This group is not moderated.)

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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#34194

On Mon, 03 Dec 2012 13:14:19 -0800, subhabangalore wrote:

> Thanks. But I am not getting the counter "5posts 0 views"...if moderator
> can please check the issue.

What counter are you talking about?

This is an email mailing list, also copied to the Usenet newsgroup 
comp.lang.python, and mirrored on other places including gmane and 
various web sites. Neither email nor Usenet include "counters", so you 
will have to explain what you are talking about.



-- 
Steven

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#34197

On Mon, 03 Dec 2012 22:11:40 +0000, Steven D'Aprano wrote:

> On Mon, 03 Dec 2012 13:14:19 -0800, subhabangalore wrote:
> 
>> Thanks. But I am not getting the counter "5posts 0 views"...if
>> moderator can please check the issue.
> 
> What counter are you talking about?
> 
> This is an email mailing list, also copied to the Usenet newsgroup
> comp.lang.python, and mirrored on other places including gmane and
> various web sites. Neither email nor Usenet include "counters", so you
> will have to explain what you are talking about.

Doubtless he is talking about G**gle Groups, since I don't see his posts 
anyway.

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#34210

On 12/03/2012 11:58 AM, subhabangalore@gmail.com wrote:
> [(1,2), (3,4)]
 >>> L=[(1,2), (3,4)]
 >>>
 >>> [b   for a in L   for b in a]
[1, 2, 3, 4]


-- 
Dr. Gary Herron
Department of Computer Science
DigiPen Institute of Technology
(425) 895-4418

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#34212

Am 03.12.2012 20:58, schrieb subhabangalore@gmail.com:
> Dear Group,
> 
> I have a tuple of list as,
> 
> tup_list=[(1,2), (3,4)]
> Now if I want to covert as a simple list,
> 
> list=[1,2,3,4]
> 
> how may I do that?

Another approach that has not yet been mentioned here:

>>> a=[(1,2), (3,4)]
>>> b=[]
>>> map(b.extend, a)
[None, None]
>>> b
[1, 2, 3, 4]

map returns [None, None] because extend returns nothing, but now
b==[1,2,3,4].

There are more ways:

>>> from operator import add
>>> reduce(add, a)
(1, 2, 3, 4)

or

>>> reduce(operator.add, (list(t) for t in a))
[1, 2, 3, 4]

I didn't do any performance testing, i guess the first one should be
about as fast es the for-loop approach with .extend() and the other two
might be quite slow. Although this only really matters if you have large
lists.

Greetings

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#34219

On 4/12/12 10:44:32, Alexander Blinne wrote:
> Am 03.12.2012 20:58, schrieb subhabangalore@gmail.com:
>> Dear Group,
>>
>> I have a tuple of list as,
>>
>> tup_list=[(1,2), (3,4)]
>> Now if I want to covert as a simple list,
>>
>> list=[1,2,3,4]
>>
>> how may I do that?
> 
> Another approach that has not yet been mentioned here:
> 
>>>> a=[(1,2), (3,4)]
>>>> b=[]
>>>> map(b.extend, a)
> [None, None]
>>>> b
> [1, 2, 3, 4]
> 
> map returns [None, None] because extend returns nothing, but now
> b==[1,2,3,4].

It's considered bad style to use map it you don't want the list it
produces.

> There are more ways:
> 
>>>> from operator import add
>>>> reduce(add, a)
> (1, 2, 3, 4)

There's a built-in that does "reduce(operator.add"; it's called "sum":

>>> sum(a, ())
(1, 2, 3, 4)
>>>
> or
> 
>>>> reduce(operator.add, (list(t) for t in a))
> [1, 2, 3, 4]

This is a valid use case for the map operator:

>>> sum(map(list, a), [])
[1, 2, 3, 4]
>>>

> I didn't do any performance testing, i guess the first one should be
> about as fast as the for-loop approach with .extend() and the other two
> might be quite slow. Although this only really matters if you have large
> lists.

Hope this helps,

-- HansM

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#34225

On 2012-12-04, Hans Mulder <hansmu@xs4all.nl> wrote:
> It's considered bad style to use map it you don't want the list it
> produces.
>
>> There are more ways:
>> 
>>>>> from operator import add
>>>>> reduce(add, a)
>> (1, 2, 3, 4)
>
> There's a built-in that does "reduce(operator.add"; it's called "sum":
>
>>>> sum(a, ())
> (1, 2, 3, 4)

I thought that sort of thing would cause a warning. Maybe it's
only for lists.

Here's the recipe from the itertools documentation:

def flatten(listOfLists):
    "Flatten one level of nesting"
    return chain.from_iterable(listOfLists)

-- 
Neil Cerutti

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