Metadata-Version: 1.1
Name: depocs
Version: 1.0.0
Summary: Scoped thread-local mixin class
Home-page: https://github.com/sdelements/depocs
Author: Security Compass
Author-email: jed@securitycompass.com
License: MIT
Description: Scoped Objects
        ==============
        
        ``Scoped`` is a mixin class that creates a thread-local stack for each of its
        subclasses. Instances of the subclass can be pushed and popped on this stack,
        and the instance at the top of the stack is always available as a property of
        the class. ``Scoped`` classes are typically used to make parameters implicitly
        available within a (dynamic) scope, without having to pass them around as
        function arguments. ``Scoped`` helps you do this in a safe and convenient way,
        and provides very informative error messages when you do something wrong.
        
        
        Examples
        --------
        
        A ``Scoped`` class can be used to pass around contextual data::
        
            class Session(Scoped):
                def __init__(self, user):
                    self.user = user
        
            def print_current_user():
                print(Session.current.user)
        
            with Session(some_guy):
                print_current_user()
        
        
        It can also be used to provide dependencies::
        
            class Clock(Scoped):
                def __init__(self, now=None):
                    self._now = now
        
                def now(self):
                    return self._now or datetime.now()
        
            Clock.default = Clock()
        
            def print_time()
                print(Clock.current.now())
        
            print_time() # Prints the real time
        
            def test_print_fake_time(self):
                with Clock(datetime(2000, 1, 1)):
                    print_time() # Prints a fake time
        
        
        Opening and Closing
        -------------------
        
        ``Scoped`` objects are best used as context managers (i.e. using the ``with``
        statement), but for situations where this isn't possible, you can also open
        and close them "manually"::
        
            class Transaction(Scoped):
                ...
        
            transaction = Transaction().open()
            try:
                ...
            finally:
                transaction.close()
        
        Obviously, you will need to do whatever is necessary to ensure that every
        call to ``open`` is matched by a call to ``close``.
        
        
        Options
        -------
        
        The behavior of ``Scoped`` subclasses can be customized by declaring
        options in a nested class named ``ScopedOptions``. Except where noted,
        options are automatically inherited by subclasses that do not override
        them::
        
            class Thingy(Scoped):
                class ScopedOptions:
        
                    # If True, instances will share the stack of their parent class.
                    # If False, this class will have its own stack independent of any
                    # ancestors. The default is to inherit the stack, unless subclassing
                    # Scoped directly. This option is NOT inherited by subclasses.
                    inherit_stack = False
        
                    # Maximum number of scopes that can be nested on this stack.
                    # This cannot be overridden if inheriting the parent stack.
                    max_nesting = 16
        
                    # If True, instances can be re-opened after being closed.
                    # If False, instances can only be opened and closed once, and will
                    # raise a LifecycleError on any attempt to reopen them.
                    allow_reuse = False
        
        
        Default Instance
        ----------------
        
        An instance of a Scoped subclass can be assigned to the ``default`` property
        of the class. This instance will be the value of the ``current`` property
        when the stack is empty i.e. when no other instances are open. The default
        instance itself is not opened by virtue of being the default. Opening it
        will push it onto the stack like any other instance.
        
        
        Errors
        ------
        
        ``Scoped`` has three inner exception classes that it will raise for various
        error conditions: ``Scoped.Error`` is the base class for the other two, which
        are ``Scoped.Missing`` and ``Scoped.Lifecycle``.
        
        ``Scoped.Missing`` is raised when an attempt is made to access a scoped object
        that is not available, i.e. when accessing ``Scoped.current`` with an empty
        stack and no default instance.
        
        ``Scoped.Lifecycle`` is raised on any attempt to open or close a scoped object
        at the wrong time e.g. opening an object that is already open, closing an object
        that is not at the top of the stack, and various other cases.
        
        Both of these exceptions are automatically subclassed along with their containing
        class. Each subclass of ``Scoped`` gets its own exception classes that inherit
        from the base exceptions. This allows you to easily handle errors from particular
        scoped classes without worrying about catching unrelated errors from other scoped
        classes.
        
        
Keywords: development thread-local
Platform: UNKNOWN
Classifier: Development Status :: 4 - Beta
Classifier: Intended Audience :: Developers
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Classifier: License :: OSI Approved :: MIT License
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.6
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.2
Classifier: Programming Language :: Python :: 3.3
Classifier: Programming Language :: Python :: 3.4
