import warnings


def index(objects, attr):
    """
    Generate a mapping of a list of objects indexed by the given attr.

    Parameters
    ----------
    objects : :class:`list`, iterable
    attr : string
        The attribute to index the list of objects by

    Returns
    -------
    dictionary : dict
        keys are the value of each object's attr, and values are from objects

    Example
    -------

    class Person(object):
        def __init__(self, name, email, age):
            self.name = name
            self.email = email
            self.age = age

    people = [
        Person('one', 'one@people.com', 1),
        Person('two', 'two@people.com', 2),
        Person('three', 'three@people.com', 3)
    ]

    by_email = index(people, 'email')
    by_name = index(people, 'name')

    assert by_name['one'] is people[0]
    assert by_email['two@people.com'] is people[1]

    """
    with warnings.catch_warnings():
        warnings.simplefilter("ignore")
        return {getattr(obj, attr): obj for obj in objects}