"""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)
[docs]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
[docs]def print_live_refs(*a, **kw):
"""Print tracked objects"""
print(format_live_refs(*a, **kw))
[docs]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]
[docs]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)