Source code for scrapy.utils.trackref

"""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).
"""

import weakref
from time import time
from operator import itemgetter
from collections import defaultdict


NoneType = type(None)
live_refs = defaultdict(weakref.WeakKeyDictionary)


[docs]class object_ref: """Inherit from this class 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(live_refs.items(), key=lambda x: x[0].__name__): if not wdict: continue if issubclass(cls, ignore): continue oldest = min(wdict.values()) s += "%-30s %6d oldest: %ds ago\n" % ( cls.__name__, len(wdict), now - oldest ) return s
[docs]def get_oldest(class_name): """Get the oldest object for a specific class name""" for cls, wdict in live_refs.items(): if cls.__name__ == class_name: if not wdict: break return min(wdict.items(), 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 live_refs.items(): if cls.__name__ == class_name: return wdict.keys()