Tooltron

"""

Generally helpful utility functions.

"""

def _ask_for_it_by_name(name):

    "Returns an object referenced by absolute path."

    bits = name.split(".")

    ## what if there is no absolute reference?

    if len(bits)>1:

        modulename = ".".join(bits[:-1])

    else:

        modulename=bits[0]

    module = __import__(modulename, {}, {}, bits[-1])

    if len(bits) == 1:

        return module

    else:

        return getattr(module, bits[-1])

def ask_for_it_by_name(name):

    "Returns an object referenced by absolute path. (Memoised outer wrapper)"

    if name not in ask_for_it_by_name.cache:

        ask_for_it_by_name.cache[name] = _ask_for_it_by_name(name)

    return ask_for_it_by_name.cache[name]

ask_for_it_by_name.cache = {}

def get_attribute(item, attribute):

    """

    Like getattr, but recursive (i.e. you can ask for 'foo.bar.yay'.)

    """

    value = item

    for part in attribute.split("."):

        value = getattr(value, part)

    return value

def auto_through(field):

    "Returns if the M2M class passed in has an autogenerated through table or not."

    return (

        # Django 1.0/1.1

        (not field.rel.through)

        or

        # Django 1.2+

        getattr(getattr(field.rel.through, "_meta", None), "auto_created", False)

    )

def auto_model(model):

    "Returns if the given model was automatically generated."

    return getattr(model._meta, "auto_created", False)

def memoize(function):

    "Standard memoization decorator."

    name = function.__name__

    _name = '_' + name

    def method(self):

        if not hasattr(self, _name):

            value = function(self)

            setattr(self, _name, value)

        return getattr(self, _name)

    def invalidate():

        if hasattr(method, _name):

            delattr(method, _name)

    method.__name__ = function.__name__

    method.__doc__ = function.__doc__

    method._invalidate = invalidate

    return method