Created
May 22, 2015 19:37
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a proxy wrapper for objects that lazily creates object copies on simple attribution of the object to other variables.
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# copyright Joao S. O. Bueno (2015) | |
# License: # SVP write me if you intend to reuse stuff here for anything but mayhem | |
# There is an LGPL with lazyobjects based on this idea for proxy at | |
# bitbucket.org/jsbueno/metapython [lazy_decorator.py] | |
# NB: although there is support for inspecting Frames - this works only | |
# for global variables | |
# working for Python2 - for python3 onlye the metaclass usage should need to be changed | |
import gc, types | |
from copy import copy | |
from functools import wraps | |
data_model_methods = """ | |
__repr__ __str__ __cmp__ | |
__hash__ __nonzero__ | |
__delattr__ | |
__call__ | |
__len__ __getitem__ __setitem__ __delitem__ __reversed__ __contains__ | |
__add__ __sub__ __mul__ __floordiv__ __mod__ __divmod__ __pow__ __div__ __truediv__ | |
__lshift__ __rshift__ __and__ __xor__ __or__ | |
__radd__ __rsub__ __rmul__ __rfloordiv__ __rmod__ __rdivmod__ | |
__rpow__ __rdiv__ __rtruediv__ | |
__rlshift__ __rrshift__ __rand__ __rxor__ __ror__ | |
__iadd__ __isub__ __imul__ __ifloordiv__ __imod__ __ipow__ __idiv__ __itruediv__ | |
__ilshift__ __irshift__ __iand__ __ixor__ __ior__ | |
__neg__ __pos__ __abs__ __invert__ | |
__complex__ __int__ __long__ __float__ | |
__oct__ __hex__ | |
__index__ __coerce__ | |
""".split() | |
def auto_copy_decorator(method): | |
wraps(method) | |
instances = {} | |
def wrapper(self, *args, **kw): | |
self = self._do_the_thing() | |
return getattr(self._proxied.__class__, method)(self._proxied, *args, **kw) | |
return wrapper | |
class MetaAutoCopyProxy(type): | |
def __new__(metacls, name, bases, dct): | |
for key in data_model_methods: | |
dct[key] = auto_copy_decorator(key) | |
return type.__new__(metacls, name, bases, dct) | |
class AutoCopyProxy(object): | |
__metaclass__ = MetaAutoCopyProxy | |
def __init__(self, proxied): | |
self._proxied = proxied | |
self._instances = {} | |
def _do_the_thing(self): | |
first_copy = True | |
new_self = self | |
for ref in gc.get_referrers(self): | |
if isinstance(ref, types.FrameType): | |
ref = ref.f_locals | |
elif isinstance(ref, dict): | |
pass | |
else: | |
continue | |
for key, value in ref.items(): | |
if value is self: | |
if first_copy: | |
first_copy = False | |
continue | |
new_self = AutoCopyProxy(copy(self._proxied)) | |
# Changeling thing: | |
ref[key] = new_self | |
return new_self | |
def __getattribute__(self, attr): | |
if attr not in ("__init__", "_instances", "_proxied", "_do_the_thing"): | |
self = self._do_the_thing() | |
return getattr(self._proxied, attr) | |
return object.__getattribute__(self, attr) | |
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""" | |
>>> from autocopyproxy import AutoCopyProxy as A | |
>>> x = A([]) | |
>>> y = x | |
>>> y is x | |
True | |
>>> y.append(5) | |
>>> x | |
[] | |
>>> y | |
[5] | |
>>> y is x | |
False | |
""" |
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