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106 lines
2.6 KiB
Python
106 lines
2.6 KiB
Python
6 years ago
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"""
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Module for testing automatic garbage collection of objects
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.. autosummary::
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:toctree: generated/
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set_gc_state - enable or disable garbage collection
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gc_state - context manager for given state of garbage collector
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assert_deallocated - context manager to check for circular references on object
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"""
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import weakref
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import gc
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import sys
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from contextlib import contextmanager
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__all__ = ['set_gc_state', 'gc_state', 'assert_deallocated']
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IS_PYPY = '__pypy__' in sys.modules
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class ReferenceError(AssertionError):
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pass
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def set_gc_state(state):
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""" Set status of garbage collector """
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if gc.isenabled() == state:
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return
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if state:
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gc.enable()
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else:
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gc.disable()
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@contextmanager
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def gc_state(state):
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""" Context manager to set state of garbage collector to `state`
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Parameters
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----------
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state : bool
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True for gc enabled, False for disabled
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Examples
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--------
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>>> with gc_state(False):
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... assert not gc.isenabled()
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>>> with gc_state(True):
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... assert gc.isenabled()
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"""
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orig_state = gc.isenabled()
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set_gc_state(state)
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yield
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set_gc_state(orig_state)
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@contextmanager
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def assert_deallocated(func, *args, **kwargs):
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"""Context manager to check that object is deallocated
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This is useful for checking that an object can be freed directly by
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reference counting, without requiring gc to break reference cycles.
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GC is disabled inside the context manager.
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This check is not available on PyPy.
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Parameters
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----------
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func : callable
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Callable to create object to check
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\\*args : sequence
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positional arguments to `func` in order to create object to check
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\\*\\*kwargs : dict
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keyword arguments to `func` in order to create object to check
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Examples
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--------
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>>> class C(object): pass
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>>> with assert_deallocated(C) as c:
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... # do something
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... del c
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>>> class C(object):
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... def __init__(self):
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... self._circular = self # Make circular reference
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>>> with assert_deallocated(C) as c: #doctest: +IGNORE_EXCEPTION_DETAIL
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... # do something
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... del c
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Traceback (most recent call last):
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...
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ReferenceError: Remaining reference(s) to object
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"""
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if IS_PYPY:
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raise RuntimeError("assert_deallocated is unavailable on PyPy")
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with gc_state(False):
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obj = func(*args, **kwargs)
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ref = weakref.ref(obj)
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yield obj
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del obj
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if ref() is not None:
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raise ReferenceError("Remaining reference(s) to object")
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