Combinations of length k from set m

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Permalink Reply by Benjamin Golder on April 4, 2013 at 12:05pm

http://docs.python.org/2/library/itertools.html#itertools.combinations

I'm not sure if IronPython has itertools, but in standard python, there is an easy command for this:

import itertools

for combo in itertools.combinations(m, k):

    # do something with the combo

Permalink Reply by Benjamin Golder on April 4, 2013 at 12:07pm

itertools appears to be implemented in IronPython 2.7:

http://ironpython-test.readthedocs.org/en/latest/library/itertools....

Permalink Reply by Jackson Bewley on April 4, 2013 at 12:22pm

Benjamin,

I had seen itertools, but could not figure out how to get it to print or output the combinations.

I've attached an example file where the set is the list of numbers from 0 to 19 for use as indexes later and the k value is just 5.  The goal is to output all combinations of length 5 from the list of integers 0 to 19.

I placed the list in brackets in order to make it iterable (I don't really know what this means.)  Somehow I need to get the combinations out of the itertools.combination output.

Attachments:

• Combinations.gh, 2 KB

Permalink Reply by Jackson Bewley on April 4, 2013 at 1:55pm

At this point I have figured out the itertools so I would posit a second question, how to unpack the tuples of combinations, so that I can have a branch for each combination (each list of indices to pull from the original set).  So that ultimately each combination is in its own branch.

I cannot solve this in python but was through string manipulation, able to do so with grasshopper components. I will post the file here.

Jackson

Attachments:

• Combinations.gh, 3 KB

Permalink Reply by Benjamin Golder on April 5, 2013 at 1:18pm

In case it is helpful, here's an example of making branches on a data tree with Python:

https://gist.github.com/bengolder/1974640