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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 from 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
- from time import time
- from operator import itemgetter
- from collections import defaultdict
- import six
- 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):
- """Return a tabular representation of tracked objects"""
- s = "Live References\n\n"
- now = time()
- for cls, wdict in sorted(six.iteritems(live_refs),
- key=lambda x: x[0].__name__):
- if not wdict:
- continue
- if issubclass(cls, ignore):
- continue
- oldest = min(six.itervalues(wdict))
- s += "%-30s %6d oldest: %ds ago\n" % (
- cls.__name__, len(wdict), now - oldest
- )
- return s
- def print_live_refs(*a, **kw):
- """Print tracked objects"""
- print(format_live_refs(*a, **kw))
- def get_oldest(class_name):
- """Get the oldest object for a specific class name"""
- for cls, wdict in six.iteritems(live_refs):
- if cls.__name__ == class_name:
- if not wdict:
- break
- return min(six.iteritems(wdict), key=itemgetter(1))[0]
- def iter_all(class_name):
- """Iterate over all objects of the same class by its class name"""
- for cls, wdict in six.iteritems(live_refs):
- if cls.__name__ == class_name:
- return six.iterkeys(wdict)
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