[Tutor] Creating lists with 3 (later4) items occuring only once

[marcus lütolf]

Hi Alan G,
thanks for your quick answer.

The copy of my code below, sent  on 18/09/15 16:41 is for some reasons incomplete. It should read

>>> import string, itertools
>>> s = ['ab','ac','bc','ad','ae','de']
>>> count = 0
>>> for startlist in itertools.combinations(s, 3):
>>>     count = count + 1
>>>     stl = list(startlist)
>>>     print count, stl
>>>     for pair in s:
>>>         x = stl.count(pair)
>>>         print x, pair 

My task is to have lists containing  3 tuples, each tuple ocurring only once. In my code above I started off with 6 tuples ( = s) of which 20
lists (count) are produced containing each of the 6 tuples  multiple times.
Therefore, I try to write additional code for eliminating all lists which contain tuples occuring more than once.
If I use all 325 tuples I would first get many thousand lists. 
Your code proposal  uses dictionaries.  If I used  dictionaries with all  the 325 possible tuples I would have to do a lot of typing and not 
getting lists with 3 tuples in it.
So, I am stuck somehow and hope to have made my tasks clear.

Thanks  for further help, Marcus.
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-----Ursprüngliche Nachricht-----
Von: Tutor [mailto:tutor-bounces+marcus.luetolf=bluewin.ch at python.org] Im Auftrag von Alan Gauld
Gesendet: Freitag, 18. September 2015 18:58
An: tutor at python.org
Betreff: Re: [Tutor] Creating lists with 3 (later4) items occuring only once

On 18/09/15 16:41, marcus lütolf wrote:

>>>> s = ['ab','ac','bc','ad','ae','de'] for startlist in 
>>>> itertools.combinations(s, 3):

> How can I concatenate the 20 lists in oder to get one count for each of the items in s , for example 10 for 'ab'?


If I understand you correctly, something like this:

 >>> counts = {'ab':0,'ac':0,'bc':0,'ad':0,'ae':0,'de':0}
 >>> for combo in it.combinations(counts.keys(),3):
...     for pair in combo:
...        counts[pair] += 1
...
 >>> counts
{'ac': 10, 'ab': 10, 'ae': 10, 'ad': 10, 'bc': 10, 'de': 10}

Is that what you want?

--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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