Number Sequencing, Grouping and Filtering
Hi I was hoping someone would be able to point me in the direction of some good documentation regarding sequencing, grouping and filtering and in which order they should be done. As a small example it is easy to create the range of numbers 1 to 20. But if I wanted to group all possible combinations of sets of 4 numbers within this range is there already an in uilt function for this I am searching the module docs with number sequencing and number grouping but cannot find info. Then if I wanted to refine this results further eg no consecutive numbers to be contained in sets. Is it best to create all sets and then filter the sets for things matching this criteria or to set this condition in a creation. Creating sets and then filtering would soon become unwieldy with a larger range I would imagine.. An ideas, pointers to docs or better search terms to help me explore this further would be appreciated. Thanks Sayth -- http://mail.python.org/mailman/listinfo/python-list
Re: Number Sequencing, Grouping and Filtering
On Tue, Mar 10, 2009 at 2:54 AM, flebber flebber.c...@gmail.com wrote: Hi I was hoping someone would be able to point me in the direction of some good documentation regarding sequencing, grouping and filtering and in which order they should be done. As a small example it is easy to create the range of numbers 1 to 20. But if I wanted to group all possible combinations of sets of 4 numbers within this range is there already an in uilt function for this I am searching the module docs with number sequencing and number grouping but cannot find info. I think itertools (http://docs.python.org/library/itertools.html) combined with list comprehensions (http://docs.python.org/dev/tutorial/datastructures.html#list-comprehensions) should be able to accomplish what you want. Cheers, Chris -- I have a blog: http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Number Sequencing, Grouping and Filtering
On Mar 10, 8:54 pm, flebber flebber.c...@gmail.com wrote: Hi I was hoping someone would be able to point me in the direction of some good documentation regarding sequencing, grouping and filtering and in which order they should be done. As a small example it is easy to create the range of numbers 1 to 20. But if I wanted to group all possible combinations of sets of 4 numbers within this range is there already an in uilt function for this I am searching the module docs with number sequencing and number grouping but cannot find info. Then if I wanted to refine this results further eg no consecutive numbers to be contained in sets. Is it best to create all sets and then filter the sets for things matching this criteria or to set this condition in a creation. Creating sets and then filtering would soon become unwieldy with a larger range I would imagine.. An ideas, pointers to docs or better search terms to help me explore this further would be appreciated. Thanks Sayth I have just found itertools is this acheivable using combinations() and groupby() in itertools? -- http://mail.python.org/mailman/listinfo/python-list
Re: Number Sequencing, Grouping and Filtering
On Tue, Mar 10, 2009 at 3:00 AM, flebber flebber.c...@gmail.com wrote: On Mar 10, 8:54 pm, flebber flebber.c...@gmail.com wrote: Hi I was hoping someone would be able to point me in the direction of some good documentation regarding sequencing, grouping and filtering and in which order they should be done. As a small example it is easy to create the range of numbers 1 to 20. But if I wanted to group all possible combinations of sets of 4 numbers within this range is there already an in uilt function for this I am searching the module docs with number sequencing and number grouping but cannot find info. Then if I wanted to refine this results further eg no consecutive numbers to be contained in sets. Is it best to create all sets and then filter the sets for things matching this criteria or to set this condition in a creation. Creating sets and then filtering would soon become unwieldy with a larger range I would imagine.. An ideas, pointers to docs or better search terms to help me explore this further would be appreciated. Thanks Sayth I have just found itertools is this acheivable using combinations() and groupby() in itertools? Yes; indeed, those were the functions your post brought to mind and which led me to suggest itertools. Cheers, Chris -- I have a blog: http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Number Sequencing, Grouping and Filtering
On Mar 10, 9:07 pm, Chris Rebert c...@rebertia.com wrote: On Tue, Mar 10, 2009 at 3:00 AM, flebber flebber.c...@gmail.com wrote: On Mar 10, 8:54 pm, flebber flebber.c...@gmail.com wrote: Hi I was hoping someone would be able to point me in the direction of some good documentation regarding sequencing, grouping and filtering and in which order they should be done. As a small example it is easy to create the range of numbers 1 to 20. But if I wanted to group all possible combinations of sets of 4 numbers within this range is there already an in uilt function for this I am searching the module docs with number sequencing and number grouping but cannot find info. Then if I wanted to refine this results further eg no consecutive numbers to be contained in sets. Is it best to create all sets and then filter the sets for things matching this criteria or to set this condition in a creation. Creating sets and then filtering would soon become unwieldy with a larger range I would imagine.. An ideas, pointers to docs or better search terms to help me explore this further would be appreciated. Thanks Sayth I have just found itertools is this acheivable using combinations() and groupby() in itertools? Yes; indeed, those were the functions your post brought to mind and which led me to suggest itertools. Cheers, Chris -- I have a blog:http://blog.rebertia.com the only issue i can see is that i am using python 2.54 currently as ifelt it more supported by other programs than 2.6 or 3.0. After searching it seems that itertools has had a upgrade in 2.61 -- http://mail.python.org/mailman/listinfo/python-list
Re: Number Sequencing, Grouping and Filtering
[flebber]
the only issue i can see is that i am using python 2.54 currently as
ifelt it more supported by other programs than 2.6 or 3.0. After
searching it seems that itertools has had a upgrade in 2.61
All of the itertools include pure python equivalents in their docs,
so it should be possible to backport them to 2.5 by cutting and
pasting the code equivalent.
Raymond
-
def combinations(iterable, r):
# combinations('ABCD', 2) -- AB AC AD BC BD CD
# combinations(range(4), 3) -- 012 013 023 123
pool = tuple(iterable)
n = len(pool)
indices = range(r)
yield tuple(pool[i] for i in indices)
while 1:
for i in reversed(range(r)):
if indices[i] != i + n - r:
break
else:
return
indices[i] += 1
for j in range(i+1, r):
indices[j] = indices[j-1] + 1
yield tuple(pool[i] for i in indices)
--
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