Documentation

As of the 0.2 release, context_tools includes three tools:

decorate_with()

decorate_with() allows you to use a context manager as a function decorator (though not a class decorator or a generator decorator. That is, 

@context_tools.decorate_with(my_manager())
def foo(context, y, z):
  ...

is equivalent to

def foo(y, z):
  with my_manager() as context:
    ...

Note that new first parameter in the decorate_with() example; the context value is passed into the function as the first parameter.

test_with()

test_with() allows you to use transform a context manager into setUp() and tearDown() function pairs for unittest- and test_harness-based test suites. That is, 

from context_tools import test_with
                    
class Test(unittest.TestCase):

  setUp, tearDown = test_with(foo_bar=my_manager(),
                              bar_baz=other_mgr())

  def test_foo(self):
    frobnicate(self.foo_bar)
    frobnicate(self.bar_baz, with_baz=True)
    self.assertEqual(frob_count, 2)

The context manager's __enter__() will be called in setUp() method, and the manager's __exit__() method will be called in tearDown(). __exit__() will always be called with (None, None, None) as arguments, even if the test raised an exception.

Note that the names of the keyword arguments supplied to test_with() will be used as the names of the instance attributes used to store the context values (foo_bar and bar_baz in the above).

yield_with()

yield_with() is like decorate_with(), except for generators. 

@context_tools.yield_with(my_manager())
def foo(context, x, y):
  ...
  yield something
  ...
  yield something_else

The context manager's __enter__() will be called when the generator function is called, and __exit__() will be called when the generator raises an exception (StopIteration or otherwise).

Like decorate_with(), the context value will be passed in as the generator function's first parameter.

Having the context manager's __exit__() method return True will not cause StopIteration to be swallowed as it would other exceptions.

context_tools