utils.py 文件源码

def first_element(obj):
    """
    Return the first element of `obj`

    Parameters
    ----------
    obj : iterable
        Should not be an iterator

    Returns
    -------
    out : object
        First element of `obj`. Raise a class:`StopIteration`
        exception if `obj` is empty.
    """
    if isinstance(obj, Iterator):
        raise RuntimeError(
            "Cannot get the first element of an iterator")
    return next(iter(obj))