Re: list comprehension (searching for onliners)
On Fri, 2006-10-20 at 10:53, Fredrik Lundh wrote: > if you want to become a good Python programmer, you really need to get > over that "I need a oneliner" idea. +1 QOTW -Carsten -- http://mail.python.org/mailman/listinfo/python-list
Re: list comprehension (searching for onliners)
Gerardo Herzig wrote: [...] > and so on...what i need to do is some list comprehension that returns me > something like [...] You don't _need_ a list comprehension, you just _want_ one :) [...] > Ill keeping blew off my hair and drinking more cofee while searching for > this damn onliner im looking for. I know, trying to put complex logic in one line makes you do all that. Go for the multiliner! -- Roberto Bonvallet -- http://mail.python.org/mailman/listinfo/python-list
Re: list comprehension (searching for onliners)
Gerardo Herzig wrote: > Thanks a lot dudes, i hope someday ill turn myself into some of you guys > who can actually answer questions ;) if you want to become a good Python programmer, you really need to get over that "I need a oneliner" idea. -- http://mail.python.org/mailman/listinfo/python-list
Re: list comprehension (searching for onliners)
Gerardo Herzig <[EMAIL PROTECTED]> writes: > You are the man, you are the man!! Yes, i need those dicts in order to > assign them to a nested for the htmltmpl templating > engine. Thats why i cant use the solution provided by Max, and thanks > to Jon too!! I'm confused, can't you write a multi-line function and pass that? -- http://mail.python.org/mailman/listinfo/python-list
Re: list comprehension (searching for onliners)
You are the man, you are the man!! Yes, i need those dicts in order to
assign them to a nested for the htmltmpl templating engine.
Thats why i cant use the solution provided by Max, and thanks to Jon too!!
Thanks a lot dudes, i hope someday ill turn myself into some of you guys
who can actually answer questions ;)
Gerardo
>> result = [{'service_id' : 1, 'value': 10},
>> {'service_id': 2, 'value': 5},
>> {'service_id': 1, 'value': 15},
>> {'service_id': 2, 'value': 15},
>> ]
>>
>> and so on...what i need to do is some list comprehension that returns
>> me something like
>>
>> result = [
>> {
>> 'service_id' : 1, 'values': [ {'value': 10},
>> {'value': 15}]
>> },
>> {
>> 'service_id' : 2, 'values': [ {'value': 5}, {'value': 15}]
>> }
>>
>> My problem now is i cant avoid have "repeteated" entries, lets say,
>> in this particular case, 2 entries for "service_id = 1", and other 2
>> for "service_id =2".
>
>
> Okay...while I'm not sure the opacity of a one-liner is actually
> productive, it *can* be done. Whether it should, I leave that to your
> discernment. :)
>
> >>> [{'service_id': i, 'values':[{'value':d2['value']} for d2 in
> result if d2['service_id'] == i ]} for i in set(d['service_id'] for d
> in result)]
>
> [{'service_id': 1, 'values': [{'value': 10}, {'value': 15}]},
> {'service_id': 2, 'values': [{'value': 5}, {'value': 15}]}]
>
>
> There's no claiming it's efficient, as it looks like there may be some
> O(N^2) logic going on under the hood (or possibly O(N*M) where N is
> the size of the result-set and M is the count of unique service_id
> values), as it's iterating over the result-set in two
> dimensions...once to create the set of top-level indices, and once for
> each result.
>
> If you didn't have to have all those dictionaries around, it might
> come out more cleanly to just have some result-set that came out to be
>
> {1: [10,15], 2: [5,15]}
>
> Just a few thoughts...
>
> -tkc
>
>
>
>
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Re: list comprehension (searching for onliners)
Gerardo Herzig wrote:
> Hi all: I have this list thing as a result of a db.query: (short version)
> result = [{'service_id' : 1, 'value': 10},
> {'service_id': 2, 'value': 5},
> {'service_id': 1, 'value': 15},
> {'service_id': 2, 'value': 15},
> ]
>
> and so on...what i need to do is some list comprehension that returns me
> something like
>
> result = [
> {
> 'service_id' : 1, 'values': [ {'value': 10},
> {'value': 15}]
> },
> {
> 'service_id' : 2, 'values': [ {'value': 5}, {'value': 15}]
> }
>
>
> My problem now is i cant avoid have "repeteated" entries, lets say, in
> this particular case, 2 entries for "service_id = 1", and other 2 for
> "service_id =2".
> Ill keeping blew off my hair and drinking more cofee while searching for
> this damn onliner im looking for.
If you import itertools and have your DB query return in order of
service_id (or sort the list after retrieving result), then...
[ [dict(service_id=key),[dict(value=n['value']) for n in value]] for
key,value in itertools.groupby(result,lambda x: x['service_id']) ]
... is more or less what you want.
Jon.
--
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Re: list comprehension (searching for onliners)
> result = [{'service_id' : 1, 'value': 10},
> {'service_id': 2, 'value': 5},
> {'service_id': 1, 'value': 15},
> {'service_id': 2, 'value': 15},
> ]
>
> and so on...what i need to do is some list comprehension that returns me
> something like
>
> result = [
> {
> 'service_id' : 1, 'values': [ {'value': 10},
> {'value': 15}]
> },
> {
> 'service_id' : 2, 'values': [ {'value': 5}, {'value': 15}]
> }
>
>
> My problem now is i cant avoid have "repeteated" entries, lets say, in
> this particular case, 2 entries for "service_id = 1", and other 2 for
> "service_id =2".
Okay...while I'm not sure the opacity of a one-liner is actually
productive, it *can* be done. Whether it should, I leave that to
your discernment. :)
>>> [{'service_id': i, 'values':[{'value':d2['value']} for d2 in
result if d2['service_id'] == i ]} for i in set(d['service_id']
for d in result)]
[{'service_id': 1, 'values': [{'value': 10}, {'value': 15}]},
{'service_id': 2, 'values': [{'value': 5}, {'value': 15}]}]
There's no claiming it's efficient, as it looks like there may be
some O(N^2) logic going on under the hood (or possibly O(N*M)
where N is the size of the result-set and M is the count of
unique service_id values), as it's iterating over the result-set
in two dimensions...once to create the set of top-level indices,
and once for each result.
If you didn't have to have all those dictionaries around, it
might come out more cleanly to just have some result-set that
came out to be
{1: [10,15], 2: [5,15]}
Just a few thoughts...
-tkc
--
http://mail.python.org/mailman/listinfo/python-list
Re: list comprehension (searching for onliners)
Gerardo Herzig <[EMAIL PROTECTED]> wrote:
> Hi all: I have this list thing as a result of a db.query: (short
> version) result = [{'service_id' : 1, 'value': 10},
> {'service_id': 2, 'value': 5},
> {'service_id': 1, 'value': 15},
> {'service_id': 2, 'value': 15},
> ]
>
> and so on...what i need to do is some list comprehension that
> returns me something like
>
> result = [
> {
> 'service_id' : 1, 'values': [ {'value': 10},
> {'value': 15}]
> },
> {
> 'service_id' : 2, 'values': [ {'value': 5},
> {'value': 15}]
> }
>
>
> My problem now is i cant avoid have "repeteated" entries, lets
> say, in this particular case, 2 entries for "service_id = 1", and
> other 2 for "service_id =2".
> Ill keeping blew off my hair and drinking more cofee while
> searching for this damn onliner im looking for.
>
> Thanks dudes.
> Gerardo
Is three lines ok?
>>> output=dict()
>>> for record in result:
output.setdefault(record['service_id'], list()).append(record
['value'])
>>> output
{1: [10, 15], 2: [5, 15]}
>>>
Creating the more verbose output that you specified should be
pretty straighforward from there.
max
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