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"""This module provides some functions and classes to record and report
references to live object instances.
If you want live objects for a particular class to be tracked, you only have to
subclass form object_ref (instead of object).
About performance: This library has a minimal performance impact when enabled,
and no performance penalty at all when disabled (as object_ref becomes just an
alias to object in that case).
"""
from __future__ import print_function
import weakref, os
from collections import defaultdict
from time import time
from operator import itemgetter
NoneType = type(None)
live_refs = defaultdict(weakref.WeakKeyDictionary)
class object_ref(object):
"""Inherit from this class (instead of object) to a keep a record of live
instances"""
__slots__ = ()
def __new__(cls, *args, **kwargs):
obj = object.__new__(cls)
live_refs[cls][obj] = time()
return obj
def format_live_refs(ignore=NoneType):
s = "Live References" + os.linesep + os.linesep
now = time()
for cls, wdict in live_refs.iteritems():
if not wdict:
continue
if issubclass(cls, ignore):
continue
oldest = min(wdict.itervalues())
s += "%-30s %6d oldest: %ds ago" % (cls.__name__, len(wdict), \
now-oldest) + os.linesep
return s
def print_live_refs(*a, **kw):
print(format_live_refs(*a, **kw))
def get_oldest(class_name):
for cls, wdict in live_refs.iteritems():
if cls.__name__ == class_name:
if wdict:
return min(wdict.iteritems(), key=itemgetter(1))[0]
def iter_all(class_name):
for cls, wdict in live_refs.iteritems():
if cls.__name__ == class_name:
return wdict.iterkeys()
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