Useful python snippets

chunk.py

from typing import Sequence


def chunks(l: Collection, n):
    """
    Yield successive n-sized chunks from l.

    >>> list(chunks([1,2,3,4,5,6], 3))
    [[1, 2, 3], [4, 5, 6]]
    >>> list(chunks([1,2,3,4,5,6], 5))
    [[1, 2, 3, 4, 5], [6]]
    """
    for i in range(0, len(l), n):
        yield l[i:i + n]

iterate_n_items.py

from typing import Sequence


def cycle_until_n(l: Sequence, n: int, start: int = 0):
    """
    Cycle the sequence until n is reached
    >>> list(cycle_until_n([1, 2, 3, 4], 6))
    [1, 2, 3, 4, 1, 2]
    """
    for i in range(n):
        # stay inside the range of the sequence
        index = (start+i) % len(l)
        yield l[index]

map_neighbor.py

def map_neighbor(values: Sequence[Any], f: Callable, d: int = 1) -> List[Any]:
    """
    Applies f to every values dth neighbor
    f(v_0, v_d) f(v_1, v_d+1), ..., f(v_n-d, v_n)
    :param values: The values f is applied on
    :param f: The callable used on the values needs to take to arguments
    :param d: The distance of the indices used, defaults to 1
    :return: List containing the resulting values, with length len(values)-1

    >>> from operator import sub
    >>> values = [1, 2, 3, 4, 5]
    >>> f = lambda a, b: abs(sub(a, b))
    >>> map_neighbor(values, f, 1)
    [1, 1, 1, 1]
    >>> map_neighbor(values, f, 2)
    [2, 2, 2]
    """
    return [f(a, b) for a, b in zip(values[:-d], values[d:])]