Code suggestion - List comprehension

[Mark Lawrence]

On 13/12/2013 09:43, Peter Otten wrote:
> Shyam Parimal Katti wrote:
>
>> Hello,
>>
>> I have a list of sql queries, some which are split across multiple list
>> elements e.x.
>> ['drop table sample_table;', 'create table sample_test', '(col1 int);',
>> 'select col1 from', ' sample_test;']
>>
>> A semi-colon in the string value  indicates the termination of a sql
>> query. So the expected out come is a conversion to a list of valid sql
>> queries:
>> ['drop table sample_table;', 'create table sample_test (col1 int);',
>> 'select col1 from sample_test;']
>>
>> Here is the code that does that:
>>
>> sample = ['drop table sample_table;', 'create table sample_test', '(col1
>> int);', 'select col1 from', ' sample_test;']
>> pure_sqls = []
>> query_holder= ''
>> for each_line in sample:
>>      query_holder += each_line
>>      if query_holder.endswith(';'):
>>          pure_sqls.append(query_holder)
>>          query_holder = ''
>>
>>
>> Is there a way to do this by eliminating explicit creation of new
>> list(pure_sqls) and a temporary variable(query_holder)? Using list
>> comprehension? Though I don't want to put the shorter version in
>> production(if it is difficult to understand), I am looking if this can be
>> done with list comprehension since I am trying to learn list comprehension
>> by using it in such scenarios.
>
> Yours is the sane approach, but it may be fun to try to understand the
> following evil hacks ;)
>
>>>> [sql.replace("\0", " ") + ";" for sql in "\0".join(sample +
> [""]).split(";\0") if sql]
> ['drop table sample_table;', 'create table sample_test (col1 int);', 'select
> col1 from  sample_test;']
>
>
>>>> from itertools import groupby
>>>> def key(x, group=[0]):
> ...     try:
> ...             return group[0]
> ...     finally:
> ...             group[0] += x.endswith(";")
> ...
>>>> [" ".join(group) for _, group in groupby(sample, key)]
> ['drop table sample_table;', 'create table sample_test (col1 int);', 'select
> col1 from  sample_test;']
>
>

Evil?  Bring back the death penalty for code like the above, that's what 
I say :)

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

Mark Lawrence