[python] import with a string

__init__.py

import_obj.py

def import_obj(str):
    """
    Import an object with dotted name ``str``.

    Use cases:
     - ``import_obj('foo.Bar')`` - equivalent to ``from foo import Bar``.
     - ``import_obj('Bar')`` - gets the object 'Bar' from the global symbol
       table.
    """
    try:
        i = str.rindex('.')
        obj_str = str[i+1:]
        mod_str = str[:i]
    except ValueError:
        # no dot; treat it as a global
        obj = globals().get(str, None)
        if not obj:
            # we use ImportError to keep error handling for callers simple
            raise ImportError
        return obj
    else:
        mod = __import__(mod_str, globals(), locals(), [obj_str])

        return getattr(mod, obj_str)