Django "with settings" helper

django_settings_utils.py

# from django.conf import settings
from functools import wraps

class _s:
  def __init__(self, a=10, b=None):
    self.a, self.b = a,b

def _override_settings(overrides):
    _orig = {}
    _missing = []
    for k, v in overrides.iteritems():
        try:
            _orig[k] = getattr(settings, k)
        except AttributeError:
            _missing.append(k)
        setattr(settings, k, v)
    return _orig, _missing

def _restore_settings(original, missing):
    for k, v in original.iteritems():
        setattr(settings, k, v)
    for key in missing:
        delattr(settings, key)

class settings_altered(object):
    def __init__(self, **overrides):
        self.overrides = overrides

    def __enter__(self):
        self.original, self.missing = _override_settings(self.overrides)
   
    def __exit__(self, exc_type, exc_value, tb):
        _restore_settings(self.original, self.missing)
    
def with_settings(**overrides):
   """Allows you to define settings that are required for this
function to work"""
   def wrapped(func):
       @wraps(func)
       def _with_settings(*args, **kwargs):
           state = _override_settings(overrides)
           try:
               return func(*args, **kwargs)
           finally:
               _restore_settings(*state)
       return _with_settings
   return wrapped

def testcase_settings(**overrides):
    def class_wrapper(cls):
        state = [None] # don't polute the class with state
        old_setup = cls.setUp
        @wraps(cls.setUp)
        def new_setup(self):
            state[0] = _override_settings(overrides)           
            return old_setup(self)
        cls.setUp = new_setup

        old_teardown = cls.tearDown
        @wraps(cls.tearDown)
        def new_teardown(self):
            try:
                return old_teardown(self)
            finally:
                _restore_settings(*state[0])
        cls.tearDown = new_teardown

        return cls
    return class_wrapper

import unittest

class AlterSettingsTests(unittest.TestCase):

    def setUp(self):
        global settings
        self.old_settings = settings
        settings = _s()

    def tearDown(self):
        global settings
        settings = self.old_settings

    def test_decorator(self):
        global settings
        @with_settings(a=666, c=13)
        def f():
           self.assertEqual(settings.a, 666) 
           self.assertEqual(settings.b, None) 
           self.assertEqual(settings.c, 13) 
        f()
        self.assertEqual(settings.a, 10) 
        self.assertEqual(settings.b, None) 
        self.assertFalse(hasattr(settings, "c")) 

    def test_context_manager(self):
        global settings
        self.assertEqual(settings.a, 10) 
        self.assertEqual(settings.b, None) 
        self.assertFalse(hasattr(settings, "c")) 
        with settings_altered(a="a", q="q"):
           self.assertEqual(settings.a, "a") 
           self.assertEqual(settings.b, None) 
           self.assertEqual(settings.q, "q") 

        self.assertEqual(settings.a, 10) 
        self.assertEqual(settings.b, None) 
        self.assertFalse(hasattr(settings, "c")) 

@testcase_settings(a=0xff, c=17)
class MetaTestCase(unittest.TestCase):
 
    def setUp(self):
        self.assertEqual(settings.a, 0xff) 
        self.assertEqual(settings.b, 15) 
        self.assertEqual(settings.c, 17) 

    def test_one(self):
        self.assertEqual(settings.a, 0xff) 
        self.assertEqual(settings.b, 15) 
        self.assertEqual(settings.c, 17) 

    def test_two(self):
        self.assertEqual(settings.a, 0xff) 
        self.assertEqual(settings.b, 15) 
        self.assertEqual(settings.c, 17) 

    def tearDown(self):
        self.assertEqual(settings.a, 0xff) 
        self.assertEqual(settings.b, 15) 
        self.assertEqual(settings.c, 17) 

if __name__ == "__main__":
    settings = _s(42, 15)
    unittest.main()
    assert settings.a == 42
    assert settings.b == 15
    assert not hasattr(settings, "c")
    assert not hasattr(settings, "q")

gistfile2.txt