Logical task for Python proggramers. Make tuple of lists. from list.

Question

Ok! So i need to make tuple of list with 2 items.

For example if i have list range(10)

I need to make tuple like this:

[(0,1),(2,3),(4,5),(6,7),(8,9)]

How can i implametnt that?

Answer 1

See the grouper recipe from the itertools docs:

from itertools import izip_longest

def grouper(n, iterable, fillvalue=None):
    """
    >>> grouper(3, 'ABCDEFG', 'x')
    ["ABC", "DEF", "Gxx"]
    """
    args = [iter(iterable)] * n
    return izip_longest(fillvalue=fillvalue, *args)

This means that you can do:

[(el[0], el[1]) for el in grouper(2, range(10))]

Or more generally:

[(el[0], el[1]) for el in grouper(2, elements)]

Answer 2

Many different ways. Just to show off a few:

As list comprehension, where l is a sequence (i.e. integer indexes): [(l[i], l[i+1]) for i in range(0,len(l),2)]

As generator function, works for all iterables:

def some_meaningful_name(it):
    it = iter(it)
    while True:
        yield next(it), next(it)

Naive via list slicing (sucksy performance for larger lists) and copying, again using list comprehension: [pair for pair in zip(l[::2],l[1::2])].

I like the second best, and it's propably the most pythonic and generic (and since it's a generator, it runs in constant space).

Answer 3

Can also be done with numpy:

import numpy
elements = range(10)

elements = [tuple(e) for e in numpy.array(elements).reshape(-1,2).tolist()]
# [(0, 1), (2, 3), (4, 5), (6, 7), (8, 9)]