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EDITING: _itertools.py

# from more_itertools 9.0
def only(iterable, default=None, too_long=None):
    """If *iterable* has only one item, return it.
    If it has zero items, return *default*.
    If it has more than one item, raise the exception given by *too_long*,
    which is ``ValueError`` by default.
    >>> only([], default='missing')
    'missing'
    >>> only([1])
    1
    >>> only([1, 2])  # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
    ...
    ValueError: Expected exactly one item in iterable, but got 1, 2,
     and perhaps more.'
    >>> only([1, 2], too_long=TypeError)  # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
    ...
    TypeError
    Note that :func:`only` attempts to advance *iterable* twice to ensure there
    is only one item.  See :func:`spy` or :func:`peekable` to check
    iterable contents less destructively.
    """
    it = iter(iterable)
    first_value = next(it, default)

try:
        second_value = next(it)
    except StopIteration:
        pass
    else:
        msg = (
            'Expected exactly one item in iterable, but got {!r}, {!r}, '
            'and perhaps more.'.format(first_value, second_value)
        )
        raise too_long or ValueError(msg)

return first_value

CANCEL

Name	Type	Size	Modified	Actions
↩ ..	DIR	—	—
📁 __pycache__/	DIR	—	2026-04-10 04:18
📄 __init__.py	PY	506 B	2026-03-03 12:15	EDIT
📄 _adapters.py	PY	4.4 KB	2026-03-03 12:15	EDIT
📄 _common.py	PY	5.3 KB	2026-03-03 12:15	EDIT
📄 _itertools.py	PY	1.2 KB	2026-03-03 12:15	EDIT
📄 _legacy.py	PY	3.4 KB	2026-03-03 12:15	EDIT
📄 abc.py	PY	5.1 KB	2026-03-03 12:15	EDIT
📄 readers.py	PY	4.2 KB	2026-03-03 12:15	EDIT
📄 simple.py	PY	2.5 KB	2026-03-03 12:15	EDIT