08-01-2010 tiago almeida <tiago.b.alme...@gmail.com> wrote:
Hello all,
I'd like to ask how you'd implement a function *f* that transforms a
list of elements into a list of lists of elements by grouping
contiguous elements together.
Examples:
a=[1,2,3,4,5]
print( f(a, 2) ) # -> [ [1, 2], [3, 4], [5] ]
print( f(a, 3) ) # -> [ [1, 2, 3], [4, 5] ]
print( f(a, 1) ) # -> [ [1], [2], [3], [4], [5] ]
I have done a small function that does this using a while loop but
what I'm looking for is a more *pythonic* way to do this. Maybe
some function in some standard Module does this and I don't know?
[In Python 2.x]
>>> s = [1,2,3,4,5]
>>> zip(*[iter(s)]*3) # zip truncates result
[(1, 2, 3)]
>>> zip(*[iter(s)]*2)
[(1, 2), (3, 4)]
>>> zip(*[iter(s)]*3) # or simpler: zip(s) :-)
[(1,), (2,), (3,), (4,), (5,)]
>>> map(None, *[iter(s)]*2) # map fills result with None
[(1, 2), (3, 4), (5, None)]
>>> map(None, *[iter(s)]*3)
[(1, 2, 3), (4, 5, None)]
Instead of map, you can use izip_longest from itertools module:
>>> list(itertools.izip_longest(*[iter(s)]*3))
[(1, 2, 3), (4, 5, None)]
>>> list(itertools.izip_longest(*[iter(s)]*2))
[(1, 2), (3, 4), (5, None)]
See:
http://docs.python.org/library/functions.html#zip
http://docs.python.org/library/functions.html#map
http://docs.python.org/library/itertools.html#itertools.izip_longest
Cheers,
*j
--
Jan Kaliszewski (zuo) <z...@chopin.edu.pl>
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