Metadata-Version: 2.1
Name: proxytypes3
Version: 1.0.1
Summary: General purpose proxy and wrapper types.
Home-page: https://github.com/chrisspen/ProxyTypes3
Author: Chris Spencer
Author-email: chrisspen@gmail.com
License: MIT
Description: Simple Proxy Types
        ==================
        
        [![](https://img.shields.io/pypi/v/proxytypes3.svg)](https://pypi.python.org/pypi/proxytypes3) [![Build Status](https://img.shields.io/travis/chrisspen/proxytypes3.svg?branch=master)](https://travis-ci.org/chrisspen/proxytypes3)
        
        The `proxytypes3` package provides some useful base classes for creating
        proxies and wrappers for ordinary Python objects.  Proxy objects automatically
        delegate all attribute access and operations to the proxied object.  Wrappers
        are similar, but can be subclassed to allow additional attributes and
        operations to be added to the wrapped object.
        
        Note that these proxy types are not intended to be tamper-proof; the unproxied
        form of an object can be readily accessed using a proxy's `__subject__`
        attribute, and some proxy types even allow this attribute to be set.  (This can
        be handy for algorithms that lazily create circular structures and thus need to
        be able to hand out "forward reference" proxies.)
        
        This package is a fork of the [peak.util.proxies](https://pypi.org/project/ProxyTypes/) module,
        extended to include support for Python 3.* as well as better testing and continuous integration.
        
        Proxy Basics
        ------------
        
        Here's a quick demo of the `ObjectProxy` type::
        
            >>> from proxytypes3 import ObjectProxy
            >>> p = ObjectProxy(42)
        
            >>> p
            42
        
            >>> isinstance(p, int)
            True
        
            >>> p.__class__
            <... 'int'>
        
            >>> p*2
            84
        
            >>> 'X' * p
            'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
        
            >>> hex(p)
            '0x2a'
        
            >>> chr(p)
            '*'
        
            >>> p ^ 1
            43
        
            >>> p ** 2
            1764
        
        
        As you can see, a proxy is virtually indistinguishable from the object it
        proxies, except via its `__subject__` attribute, and its `type()`::
        
            >>> p.__subject__
            42
        
            >>> type(p)
            <class 'proxytypes3.proxies.ObjectProxy'>
        
        You can change the `__subject__` of an `ObjectProxy`, and it will then
        refer to something else::
        
            >>> p.__subject__ = 99
            >>> p
            99
            >>> p-33
            66
        
            >>> p.__subject__ = "foo"
            >>> p
            'foo'
        
        All operations are delegated to the subject, including setattr and delattr::
        
            >>> class Dummy: pass
            >>> d = Dummy()
            >>> p = ObjectProxy(d)
        
            >>> p.foo = "bar"
            >>> d.foo
            'bar'
        
            >>> del p.foo
            >>> hasattr(d,'foo')
            False
        
        
        Callback Proxies
        ----------------
        
        Sometimes, you may want a proxy's subject to be determined dynamically whenever
        the proxy is used.  For this purpose, you can use the `CallbackProxy` type,
        which accepts a callback function and creates a proxy that will invoke the
        callback in order to get the target.  Here's a quick example of a counter
        that gets incremented each time it's used, from zero to three::
        
            >>> from proxytypes3 import CallbackProxy
        
            >>> ct = -1
            >>> def callback():
            ...     global ct
            ...     if ct == 3: raise StopIteration
            ...     ct += 1
            ...     return ct
        
            >>> counter = CallbackProxy(callback)
        
            >>> counter
            0
            >>> counter
            1
            >>> str(counter)
            '2'
            >>> hex(counter)
            '0x3'
        
            >>> counter
            Traceback (most recent call last):
              ...
            StopIteration
        
        As you can see, the callback is automatically invoked on any attempt to use the
        proxy.  This is a somewhat silly example; a better one would be something like
        a `thread_id` proxy that is always equal to the ID # of the thread it's
        running in.
        
        A callback proxy's callback can be obtained or changed via the `get_callback`
        and `set_callback` functions::
        
            >>> from proxytypes3 import get_callback, set_callback
            >>> set_callback(counter, lambda: 42)
        
            >>> counter
            42
        
            >>> get_callback(counter)
            <function <lambda> at ...>
        
        
        Lazy Proxies
        ------------
        
        A `LazyProxy` is similar to a `CallbackProxy`, but its callback is called
        at most once, and then cached::
        
            >>> from proxytypes3 import LazyProxy
        
            >>> def callback():
            ...     print("called!")
            ...     return 42
        
            >>> lazy = LazyProxy(callback)
            >>> lazy
            called!
            42
            >>> lazy
            42
        
        You can use the `get_callback` and `set_callback` functions on lazy
        proxies, but it has no effect if the callback was already called::
        
            >>> set_callback(lazy, lambda: 99)
            >>> lazy
            42
        
        But you can use the `get_cache` and `set_cache` functions to tamper with
        the cached value::
        
            >>> from proxytypes3 import get_cache, set_cache
            >>> get_cache(lazy)
            42
            >>> set_cache(lazy, 99)
            >>> lazy
            99
        
        
        Wrappers
        --------
        
        The `ObjectWrapper`, `CallbackWrapper` and `LazyWrapper` classes are
        similar to their proxy counterparts, except that they are intended to be
        subclassed in order to add custom extra attributes or methods.  Any attribute
        that exists in a subclass of these classes will be read or written from the
        wrapper instance, instead of the wrapped object.  For example::
        
            >>> from proxytypes3 import ObjectWrapper
            >>> class NameWrapper(ObjectWrapper):
            ...     name = None
            ...     def __init__(self, ob, name):
            ...         ObjectWrapper.__init__(self, ob)
            ...         self.name = name
            ...     def __str__(self):
            ...         return self.name
        
            >>> w = NameWrapper(42, "The Ultimate Answer")
            >>> w
            42
        
            >>> print(w)
            The Ultimate Answer
        
            >>> w * 2
            84
        
            >>> w.name
            'The Ultimate Answer'
        
        Notice that any attributes you add must be defined *in the class*.  You can't
        add arbitary attributes at runtime, because they'll be set on the wrapped
        object instead of the wrapper::
        
            >>> w.foo = 'bar'
            Traceback (most recent call last):
              ...
            AttributeError: 'int' object has no attribute 'foo'
        
        Note that this means that all instance attributes must be implemented as either
        slots, properties, or have a default value defined in the class body (like the
        `name = None` shown in the example above).
        
        The `CallbackWrapper` and `LazyWrapper` base classes are basically the same
        as `ObjectWrapper`, except that they use a callback or cached lazy callback
        instead of expecting an object as their subject.
        
        
        Creating Custom Subclasses and Mixins
        -------------------------------------
        
        In addition to all the concrete classes described above, there are also two
        abstract base classes: `AbstractProxy` and `AbstractWrapper`.  If you want
        to create a mixin type that can be used with any of the concrete types, you
        should subclass the abstract version and set `__slots__` to an empty list::
        
            >>> from proxytypes3 import AbstractWrapper
        
            >>> class NamedMixin(AbstractWrapper):
            ...     __slots__ = []
            ...     name = None
            ...     def __init__(self, ob, name):
            ...         super(NamedMixin, self).__init__(ob)
            ...         self.name = name
            ...     def __str__(self):
            ...         return self.name
        
        Then, when you mix it in with the respective base class, you can add back in
        any necessary slots, or leave off `__slots__` to give the subclass instances
        a dictionary of their own::
        
            >>> from proxytypes3 import CallbackWrapper, LazyWrapper
        
            >>> class NamedObject(NamedMixin, ObjectWrapper): pass
            >>> class NamedCallback(NamedMixin, CallbackWrapper): pass
            >>> class NamedLazy(NamedMixin, LazyWrapper): pass
        
            >>> print(NamedObject(42, "The Answer"))
            The Answer
        
            >>> n = NamedCallback(callback, "Test")
            >>> n
            called!
            42
            >>> n
            called!
            42
        
            >>> n = NamedLazy(callback, "Once")
            >>> n
            called!
            42
            >>> n
            42
        
        Both the `AbstractProxy` and `AbstractWrapper` base classes work by
        assuming that `self.__subject__` will be the wrapped or proxied object.  If
        you don't want to use any of the standard three ways of defining
        `__subject__` (i.e., as an object, callback, or lazy callback), you will need
        to subclass `AbstractProxy` or `AbstractWrapper` and provide your own
        way of defining `__subject__`.
        
        Tests
        -----
        
        To run unittests across multiple Python versions, first install the necessary Python versions. On Ubuntu, run:
        
            sudo add-apt-repository ppa:deadsnakes/ppa
            sudo apt-get update
            sudo apt-get install python-dev python3.4-minimal python3.4-dev python3.5-minimal python3.5-dev python3.6 python3.6-dev
        
        Then to run all [tests](http://tox.readthedocs.org/en/latest/):
        
            tox
        
        To run tests for a specific environment (e.g. Python 2.7):
            
            tox -e py27
        
        To run a specific test:
            
            export TESTNAME=.additional_tests; tox -e py34
            
            export TESTNAME=.TestObjectProxy.testNumbers; tox -e py36
        
Platform: UNKNOWN
Classifier: Development Status :: 6 - Mature
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Description-Content-Type: text/markdown
