Create pandas DataFrame from the sequence of same-type objects.
    When a list of labels is given then only retain those labels and
    drop the rest.

def df(objs, labels=None):
    """
    Create pandas DataFrame from the sequence of same-type objects.
    When a list of labels is given then only retain those labels and
    drop the rest.
    """
    import pandas as pd
    from .objects import Object, DynamicObject
    if objs:
        objs = list(objs)
        obj = objs[0]
        if isinstance(obj, Object):
            df = pd.DataFrame.from_records(o.tuple() for o in objs)
            df.columns = obj.__class__.defaults
        elif isinstance(obj, DynamicObject):
            df = pd.DataFrame.from_records(o.__dict__ for o in objs)
        else:
            df = pd.DataFrame.from_records(objs)
        if isinstance(obj, tuple) and hasattr(obj, '_fields'):
            # assume it's a namedtuple
            df.columns = obj.__class__._fields
    else:
        df = None
    if labels:
        exclude = [label for label in df if label not in labels]
        df = df.drop(exclude, axis=1)
    return df