impl/python.py

from typing import Any, List, Sequence, TypeVar

T = TypeVar("T")


def _whole(value: Any) -> bool:
    # bool is an int in Python; True would otherwise chunk by 1.
    return isinstance(value, int) and not isinstance(value, bool)


def chunk(items: Sequence[T], size: int) -> List[List[T]]:
    """Split ``items`` into consecutive batches of at most ``size``, in order.

    An empty list gives no batches rather than one empty batch, so a loop over
    the result never sends an empty request. A size below 1 raises: it is
    always a bug upstream, and "no limit" is the outage batching prevents.
    """
    if isinstance(items, (str, bytes)) or not isinstance(items, (list, tuple)):
        raise TypeError("chunk needs a list of items")
    if not _whole(size):
        raise TypeError("size must be a whole number, received %r" % (size,))
    if size < 1:
        raise ValueError("size must be at least 1, received %d" % (size,))

    return [list(items[start : start + size]) for start in range(0, len(items), size)]