toy list processing problem: collect similar terms
Nick Mellor
thebalancepro at gmail.com
Wed Feb 6 18:37:26 EST 2013
Oops! Not that sort stability is used in this algorithm. Was thinking of something else :-)
N
On Thursday, 7 February 2013 10:25:36 UTC+11, Nick Mellor wrote:
> Python 3 version:
>
>
>
> from collections import defaultdict
>
>
>
> data = ((0,'a','b'),(1,'c','d'),(2,'e','f'),(3,'g','h'),(1,'i','j'),(2,'k','l'),(4,'m','n'),(2,'o','p'),(4,'q','r'),(5,'s','t'))
>
>
>
> register = defaultdict(list)
>
> for number, *letters in data:
>
> register[number].extend(letters)
>
> final = []
>
> for i in sorted(register.keys()):
>
> final.append(register[i])
>
> print (final)
>
>
>
> NB sorting is "stable" in Python, so sorted() will always keep the 1's, 2's etc in the same order as they were in the unsorted list.
>
>
>
> Nick
>
>
>
> On Sunday, 26 September 2010 14:05:13 UTC+10, Xah Lee wrote:
>
> > here's a interesting toy list processing problem.
>
> >
>
> > I have a list of lists, where each sublist is labelled by
>
> > a number. I need to collect together the contents of all sublists
>
> > sharing
>
> > the same label. So if I have the list
>
> >
>
> > ((0 a b) (1 c d) (2 e f) (3 g h) (1 i j) (2 k l) (4 m n) (2 o p) (4 q
>
> > r) (5 s t))
>
> >
>
> > where the first element of each sublist is the label, I need to
>
> > produce:
>
> >
>
> > output:
>
> > ((a b) (c d i j) (e f k l o p) (g h) (m n q r) (s t))
>
> >
>
> > a Mathematica solution is here:
>
> > http://xahlee.org/UnixResource_dir/writ/notations_mma.html
>
> >
>
> > R5RS Scheme lisp solution:
>
> > http://xahlee.org/UnixResource_dir/writ/Sourav_Mukherjee_sourav.work_gmail.scm
>
> > by Sourav Mukherjee
>
> >
>
> > also, a Common Lisp solution can be found here:
>
> > http://groups.google.com/group/comp.lang.lisp/browse_frm/thread/5d1ded8824bc750b?
>
> >
>
> > anyone care to give a solution in Python, Perl, javascript, or other
>
> > lang? am guessing the scheme solution can be much improved... perhaps
>
> > using some lib but that seems to show scheme is pretty weak if the lib
>
> > is non-standard.
>
> >
>
> > Xah ∑ xahlee.org ☄
More information about the Python-list
mailing list