trace_object_references

lsst.utils.introspection.trace_object_references(target_class: type, count: int = 5, max_level: int = 10) → tuple[list[list], bool]

Find the chain(s) of references that make(s) objects of a class reachable.

Parameters:

target_classtype

The class whose objects need to be traced. This is typically a class that is known to be leaking.

countint, optional

The number of example objects to trace, if that many exist.

max_levelint, optional

The number of levels of references to trace. max_level=1 means finding only objects that directly refer to the examples.

Returns:

traceslist [list]

A sequence whose first element (index 0) is the set of example objects of type target_class, whose second element (index 1) is the set of objects that refer to the examples, and so on. Contains at most max_level + 1 elements.

trace_completebool

True if the trace for all objects terminated in at most max_level references, and False if more references exist.

Examples

An example with two levels of references:

>>> from collections import namedtuple
>>> class Foo:
...     pass
>>> holder = namedtuple("Holder", ["bar", "baz"])
>>> myholder = holder(bar={"object": Foo()}, baz=42)
>>> # In doctest, the trace extends up to the whole global dict
>>> # if you let it.
>>> trace_object_references(Foo, max_level=2)  
...                                      
([[<lsst.utils.introspection.Foo object at ...>],
  [{'object': <lsst.utils.introspection.Foo object at ...>}],
  [Holder(bar={'object': <lsst.utils.introspection.Foo object at ...>},
          baz=42)]], False)