Slicing iterables in sub-generators without loosing elements
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From:
Thomas Bach <thb... @students.uni-mainz.de> Date: Sat, 29 Sep 2012 18:14:38 +0200
Local: Sat, Sep 29 2012 12:14 pm
Subject: Slicing iterables in sub-generators without loosing elements
Hi,
say we have the following:
>>> data = [('foo', 1), ('foo', 2), ('bar', 3), ('bar', 2)]
is there a way to code a function iter_in_blocks such that
>>> result = [ list(block) for block in iter_in_blocks(data) ]
evaluates to
>>> result = [ [('foo', 1), ('foo', 2)], [('bar', 3), ('bar', 2)] ]
by _only_ _iterating_ over the list (caching all the elements sharing
I came up with the following
def iter_in_blocks(iterable):
which does not work as itertools.takewhile consumes the first entry
I currently have the intuition that the problem is not solvable
Regards,
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From:
Paul Rubin <no.em... @nospam.invalid> Date: Sat, 29 Sep 2012 09:26:00 -0700
Subject: Re: Slicing iterables in sub-generators without loosing elements
Thomas Bach <thb
... @students.uni-mainz.de> writes:
>>>> result = [ [('foo', 1), ('foo', 2)], [('bar', 3), ('bar', 2)] ]
> by _only_ _iterating_ over the list (caching all the elements sharing
> the same first element doesn't count)?
is basically what you want.
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From:
Ian Kelly <ian.g.ke... @gmail.com> Date: Sat, 29 Sep 2012 10:36:39 -0600
Local: Sat, Sep 29 2012 12:36 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Sat, Sep 29, 2012 at 10:14 AM, Thomas Bach
<thb
... @students.uni-mainz.de> wrote:
> Hi,
> say we have the following:
>>>> data = [('foo', 1), ('foo', 2), ('bar', 3), ('bar', 2)]
> is there a way to code a function iter_in_blocks such that
>>>> result = [ list(block) for block in iter_in_blocks(data) ]
> evaluates to
>>>> result = [ [('foo', 1), ('foo', 2)], [('bar', 3), ('bar', 2)] ]
> by _only_ _iterating_ over the list (caching all the elements sharing
Is it guaranteed that the blocks will be contiguous? If so, you could
from itertools import groupby, imap
def iter_in_blocks(data):
If there is no such guarantee, then the list would need to be sorted first.
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From:
Thomas Bach <thb... @students.uni-mainz.de> Date: Sat, 29 Sep 2012 18:44:51 +0200
Local: Sat, Sep 29 2012 12:44 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Sat, Sep 29, 2012 at 09:26:00AM -0700, Paul Rubin wrote:
> Thomas Bach <thb
... @students.uni-mainz.de> writes:
> itertools.groupby(data, lambda (x,y) : x)
> is basically what you want.
Thanks,
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From:
88888 Dihedral <dihedral88... @googlemail.com> Date: Sun, 30 Sep 2012 17:58:39 -0700 (PDT)
Local: Sun, Sep 30 2012 8:58 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Sunday, September 30, 2012 12:15:57 AM UTC+8, Thomas Bach wrote:
> Hi,
> say we have the following:
> >>> data = [('foo', 1), ('foo', 2), ('bar', 3), ('bar', 2)]
> is there a way to code a function iter_in_blocks such that
> >>> result = [ list(block) for block in iter_in_blocks(data) ]
> evaluates to
> >>> result = [ [('foo', 1), ('foo', 2)], [('bar', 3), ('bar', 2)] ]
> by _only_ _iterating_ over the list (caching all the elements sharing
> the same first element doesn't count)?
> I came up with the following
> def iter_in_blocks(iterable):
> my_iter = iter(iterable)
> while True:
> first = next(my_iter)
> pred = lambda entry: entry[0] == first[0]
> def block_iter():
> yield first
> for entry in itertools.takewhile(pred, my_iter):
> yield entry
> yield block_iter()
> which does not work as itertools.takewhile consumes the first entry
> not fulfilling the pred.
> I currently have the intuition that the problem is not solvable
> without using e.g. a global to pass something back to iter_in_blocks
> from block_iter. Any other suggestions?
> Regards,
> Thomas Bach.
For example:
data = [('foo', 1), ('foo', 2), ('bar', 3), ('bar', 2)]
for item in data:
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From:
88888 Dihedral <dihedral88... @googlemail.com> Date: Sun, 30 Sep 2012 17:58:39 -0700 (PDT)
Local: Sun, Sep 30 2012 8:58 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Sunday, September 30, 2012 12:15:57 AM UTC+8, Thomas Bach wrote:
> Hi,
> say we have the following:
> >>> data = [('foo', 1), ('foo', 2), ('bar', 3), ('bar', 2)]
> is there a way to code a function iter_in_blocks such that
> >>> result = [ list(block) for block in iter_in_blocks(data) ]
> evaluates to
> >>> result = [ [('foo', 1), ('foo', 2)], [('bar', 3), ('bar', 2)] ]
> by _only_ _iterating_ over the list (caching all the elements sharing
> the same first element doesn't count)?
> I came up with the following
> def iter_in_blocks(iterable):
> my_iter = iter(iterable)
> while True:
> first = next(my_iter)
> pred = lambda entry: entry[0] == first[0]
> def block_iter():
> yield first
> for entry in itertools.takewhile(pred, my_iter):
> yield entry
> yield block_iter()
> which does not work as itertools.takewhile consumes the first entry
> not fulfilling the pred.
> I currently have the intuition that the problem is not solvable
> without using e.g. a global to pass something back to iter_in_blocks
> from block_iter. Any other suggestions?
> Regards,
> Thomas Bach.
For example:
data = [('foo', 1), ('foo', 2), ('bar', 3), ('bar', 2)]
for item in data:
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From:
Mark Lawrence <breamore... @yahoo.co.uk> Date: Mon, 01 Oct 2012 09:19:37 +0100
Local: Mon, Oct 1 2012 4:19 am
Subject: Re: Slicing iterables in sub-generators without loosing elements
On 01/10/2012 01:58, 88888 Dihedral wrote:
> Your question seems vague to me. If you know you are storing
--
Mark Lawrence.
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From:
Ramchandra Apte <maniandra... @gmail.com> Date: Tue, 2 Oct 2012 09:12:04 -0700 (PDT)
Local: Tues, Oct 2 2012 12:12 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Monday, 1 October 2012 13:47:50 UTC+5:30, Mark Lawrence wrote:
> On 01/10/2012 01:58, 88888 Dihedral wrote:
> > Your question seems vague to me. If you know you are storing
> > only immutable tuples in a list, then the way to iterate is simple.
> Does Python have a magic method that let's me use mutable tuples? I'd
> also like immutable lists. Is it worth raising a feature request on the
> bug tracker?
> --
> Cheers.
> Mark Lawrence.
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From:
Ramchandra Apte <maniandra... @gmail.com> Date: Tue, 2 Oct 2012 09:12:04 -0700 (PDT)
Local: Tues, Oct 2 2012 12:12 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Monday, 1 October 2012 13:47:50 UTC+5:30, Mark Lawrence wrote:
> On 01/10/2012 01:58, 88888 Dihedral wrote:
> > Your question seems vague to me. If you know you are storing
> > only immutable tuples in a list, then the way to iterate is simple.
> Does Python have a magic method that let's me use mutable tuples? I'd
> also like immutable lists. Is it worth raising a feature request on the
> bug tracker?
> --
> Cheers.
> Mark Lawrence.
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From:
Mark Lawrence <breamore... @yahoo.co.uk> Date: Tue, 02 Oct 2012 17:44:45 +0100
Local: Tues, Oct 2 2012 12:44 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On 02/10/2012 17:12, Ramchandra Apte wrote:
> On Monday, 1 October 2012 13:47:50 UTC+5:30, Mark Lawrence wrote:
>> On 01/10/2012 01:58, 88888 Dihedral wrote:
>>> Your question seems vague to me. If you know you are storing
>>> only immutable tuples in a list, then the way to iterate is simple.
>> Does Python have a magic method that let's me use mutable tuples? I'd
>> also like immutable lists. Is it worth raising a feature request on the
>> bug tracker?
>> --
>> Cheers.
>> Mark Lawrence.
> Mark, you are talking to a bot.
--
Mark Lawrence.
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From:
Chris Angelico <ros... @gmail.com> Date: Wed, 3 Oct 2012 03:58:02 +1000
Local: Tues, Oct 2 2012 1:58 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Wed, Oct 3, 2012 at 2:44 AM, Mark Lawrence <breamore
... @yahoo.co.uk> wrote:
> What happened to freedom of speech? If I want to talk to a bot, I'll talk
> to a bot. Besides I'm not convinced it/he/she is a bot. Plus if you read
> my post carefully, add in several years experience of Python the language
> and Python the comedy, you might come to the conclusion that a certain
> amount of urine extraction was going on :)
One of these days I'm going to mail Dihedral a whole pile of Gilbert
Dihedral might be a bot and might not. I've come to the conclusion
ChrisA
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From:
Mark Lawrence <breamore... @yahoo.co.uk> Date: Tue, 02 Oct 2012 19:35:55 +0100
Local: Tues, Oct 2 2012 2:35 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On 02/10/2012 18:58, Chris Angelico wrote:
> Dihedral might be a bot and might not. I've come to the conclusion
> ChrisA
--
Mark Lawrence.
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From:
Terry Reedy <tjre... @udel.edu> Date: Tue, 02 Oct 2012 14:59:04 -0400
Local: Tues, Oct 2 2012 2:59 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On 10/2/2012 1:58 PM, Chris Angelico wrote:
> On Wed, Oct 3, 2012 at 2:44 AM, Mark Lawrence <breamore
... @yahoo.co.uk> wrote:
>> What happened to freedom of speech? If I want to talk to a bot, I'll talk
>> to a bot. Besides I'm not convinced it/he/she is a bot. Plus if you read
>> my post carefully, add in several years experience of Python the language
>> and Python the comedy, you might come to the conclusion that a certain
>> amount of urine extraction was going on :)
> Coupled with a bit of bot-seeding, which is always fun.
> One of these days I'm going to mail Dihedral a whole pile of Gilbert
> Dihedral might be a bot and might not. I've come to the conclusion
--
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From:
88888 Dihedral <dihedral88... @googlemail.com> Date: Tue, 2 Oct 2012 13:54:20 -0700 (PDT)
Local: Tues, Oct 2 2012 4:54 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Monday, October 1, 2012 4:17:50 PM UTC+8, Mark Lawrence wrote:
> On 01/10/2012 01:58, 88888 Dihedral wrote:
> > Your question seems vague to me. If you know you are storing
> > only immutable tuples in a list, then the way to iterate is simple.
> Does Python have a magic method that let's me use mutable tuples? I'd
> also like immutable lists. Is it worth raising a feature request on the
> bug tracker?
> --
> Cheers.
> Mark Lawrence.
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From:
88888 Dihedral <dihedral88... @googlemail.com> Date: Tue, 2 Oct 2012 13:54:20 -0700 (PDT)
Local: Tues, Oct 2 2012 4:54 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Monday, October 1, 2012 4:17:50 PM UTC+8, Mark Lawrence wrote:
> On 01/10/2012 01:58, 88888 Dihedral wrote:
> > Your question seems vague to me. If you know you are storing
> > only immutable tuples in a list, then the way to iterate is simple.
> Does Python have a magic method that let's me use mutable tuples? I'd
> also like immutable lists. Is it worth raising a feature request on the
> bug tracker?
> --
> Cheers.
> Mark Lawrence.
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From:
Steven D'Aprano <steve+comp.lang.pyt... @pearwood.info> Date: 03 Oct 2012 00:57:20 GMT
Local: Tues, Oct 2 2012 8:57 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Wed, 03 Oct 2012 03:58:02 +1000, Chris Angelico wrote:
Oh, I'm convinced that it's a bot.
The fact that Dihedral never responds to conversations about him/it is a
Mind you, some human beings fail the Turing test too:
http://northernplanets.blogspot.com.au/2006/06/failing-turing-test.html
Of course, Dihedral's creator wanted to really confound us, the
--
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From:
88888 Dihedral <dihedral88... @googlemail.com> Date: Tue, 2 Oct 2012 18:11:20 -0700 (PDT)
Local: Tues, Oct 2 2012 9:11 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
Steven D'Aprano於 2012年10月3日星期三UTC+8上午8時57分20秒寫道：
> On Wed, 03 Oct 2012 03:58:02 +1000, Chris Angelico wrote:
> > Dihedral might be a bot and might not. I've come to the conclusion that
> > it's not worth trying to find out, given that a good bot can outdo a lot
> > of humans in useful conversation.
> Oh, I'm convinced that it's a bot.
> The fact that Dihedral never responds to conversations about him/it is a
> give away: nearly all people are far to egotistical to let accusations of
> bot-hood go unchallenged. And even though its responses are grammatically
> correct, they often are semantically meaningless. Even the best AIs
> (Evie, CleverBot, Alice) don't come close to passing the Turing test. It
> helps that Dihedral only talks about computer programming, but even so,
> it has well and truly failed my personal Turing test.
> Mind you, some human beings fail the Turing test too:
> http://northernplanets.blogspot.com.au/2006/06/failing-turing-test.html
> Of course, Dihedral's creator wanted to really confound us, the
> occasional human response would probably muddy the waters sufficiently.
> --
> Steven
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From:
Steven D'Aprano <steve+comp.lang.pyt... @pearwood.info> Date: 03 Oct 2012 01:24:13 GMT
Local: Tues, Oct 2 2012 9:24 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Tue, 02 Oct 2012 18:11:20 -0700, 88888 Dihedral wrote:
I rest my case :)
I have many problems with generators. Can you tell me more about them? I
--
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From:
88888 Dihedral <dihedral88... @googlemail.com> Date: Tue, 2 Oct 2012 18:42:19 -0700 (PDT)
Local: Tues, Oct 2 2012 9:42 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
Steven D'Aprano於 2012年10月3日星期三UTC+8上午9時24分13秒寫道：
> On Tue, 02 Oct 2012 18:11:20 -0700, 88888 Dihedral wrote:
> > Steven D'Aprano於 2012年10月3日星期三UTC+8上午8時57分20秒寫道：
> >> Oh, I'm convinced that it's a bot.
> >> The fact that Dihedral never responds to conversations about him/it is
> >> a give away: nearly all people are far to egotistical to let
> >> accusations of bot-hood go unchallenged.
> [...]
> >> Of course, Dihedral's creator wanted to really confound us, the
> >> occasional human response would probably muddy the waters sufficiently.
> > Are you still not getting the generator part in Python? Do you really
> > test any generator before?
> I rest my case :)
> I have many problems with generators. Can you tell me more about them? I
> really need your help. Sometimes, when it is very cold, the diesel
> freezes and the generator raises StopIteration at the wrong place.
> --
> Steven
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From:
Ramchandra Apte <maniandra... @gmail.com> Date: Tue, 2 Oct 2012 20:21:17 -0700 (PDT)
Local: Tues, Oct 2 2012 11:21 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Tuesday, 2 October 2012 22:13:20 UTC+5:30, Mark Lawrence wrote:
> On 02/10/2012 17:12, Ramchandra Apte wrote:
> > On Monday, 1 October 2012 13:47:50 UTC+5:30, Mark Lawrence wrote:
> >> On 01/10/2012 01:58, 88888 Dihedral wrote:
> >>> Your question seems vague to me. If you know you are storing
> >>> only immutable tuples in a list, then the way to iterate is simple.
> >> Does Python have a magic method that let's me use mutable tuples? I'd
> >> also like immutable lists. Is it worth raising a feature request on the
> >> bug tracker?
> >> --
> >> Cheers.
> >> Mark Lawrence.
> > Mark, you are talking to a bot.
> What happened to freedom of speech? If I want to talk to a bot, I'll
> talk to a bot. Besides I'm not convinced it/he/she is a bot. Plus if
> you read my post carefully, add in several years experience of Python
> the language and Python the comedy, you might come to the conclusion
> that a certain amount of urine extraction was going on :)
> --
> Cheers.
> Mark Lawrence.
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From:
Ramchandra Apte <maniandra... @gmail.com> Date: Tue, 2 Oct 2012 20:21:17 -0700 (PDT)
Local: Tues, Oct 2 2012 11:21 pm
Subject: Re: Slicing iterables in sub-generators without loosing elements
On Tuesday, 2 October 2012 22:13:20 UTC+5:30, Mark Lawrence wrote:
> On 02/10/2012 17:12, Ramchandra Apte wrote:
> > On Monday, 1 October 2012 13:47:50 UTC+5:30, Mark Lawrence wrote:
> >> On 01/10/2012 01:58, 88888 Dihedral wrote:
> >>> Your question seems vague to me. If you know you are storing
> >>> only immutable tuples in a list, then the way to iterate is simple.
> >> Does Python have a magic method that let's me use mutable tuples? I'd
> >> also like immutable lists. Is it worth raising a feature request on the
> >> bug tracker?
> >> --
> >> Cheers.
> >> Mark Lawrence.
> > Mark, you are talking to a bot.
> What happened to freedom of speech? If I want to talk to a bot, I'll
> talk to a bot. Besides I'm not convinced it/he/she is a bot. Plus if
> you read my post carefully, add in several years experience of Python
> the language and Python the comedy, you might come to the conclusion
> that a certain amount of urine extraction was going on :)
> --
> Cheers.
> Mark Lawrence.
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