CODEWITHSUNDEEP
pythonlistmerge
Zee
Zee

Reputation: 31

Merging sublists

I have this list:

newlis = [[6], [3], [4], [10], [9], [1], [2], [5], [7], [0], [8]]

I want to merge every two consecutive sublists (whether they are odd or even). I tried this code: 

    while len(newlis) != 1:
        lis1=[(a + b) for a, b in zip(newlis[::2], newlis[1::2])]
        newlis=lis1
        print newlis

The result was: [[6, 3], [4, 10], [9, 1], [2, 5], [7, 0]]

How can I modify the code that it will print [[6, 3], [4, 10], [9, 1], [2, 5], [7, 0], [8]] instead?

Upvotes: 0

Views: 121

Answers (3)

Delgan
Delgan

Reputation: 19717

If you do not want to import any library, you can use this simple one liner:

result = [sum(newlis[i:i+2], []) for i in range(0, len(newlis), 2)]

Upvotes: 0

Daniel
Daniel

Reputation: 42778

Use itertools.groupby:

>>> [[w for _, q in k for w in q] for _, k in itertools.groupby(enumerate(newlis), lambda (a,b):a//2)]
[[6, 3], [4, 10], [9, 1], [2, 5], [7, 0], [8]]

Upvotes: 0

Kasravnd
Kasravnd

Reputation: 107347

You can use itertools.izip_longest (itertools.zip_longest in python 3) :

>>> from itertools import izip_longest
>>> [(a + b) if b else a for a, b in izip_longest(newlis[::2], newlis[1::2])]
[[6, 3], [4, 10], [9, 1], [2, 5], [7, 0], [8]]

This function also accept a fillvalue that you can use to fill the missed values with a costume value :

>>> [(a + b) for a, b in izip_longest(newlis[::2], newlis[1::2],fillvalue=['**'])]
[[6, 3], [4, 10], [9, 1], [2, 5], [7, 0], [8, '**']]

One another choice is using chain and islice :

>>> from itertools import islice,chain
>>> [list(chain.from_iterable(islice(newlis,i,i+2))) for i in range(0,len(newlis),2)]
[[6, 3], [4, 10], [9, 1], [2, 5], [7, 0], [8]]

Upvotes: 1

Related Questions