Find and visualise reference cycles between Python objects.

pip install refcycle==0.2.1


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The refcycle package provides support for creating, analysing, and visualising graphs of Python objects and the references between them. It's intended to aid in debugging reference-related problems, for example:

  • Figuring out why an object is still alive after it should have been deleted.
  • Detecting reference cycles that may be preventing objects from being collected by the regular reference-count-based garbage collection.
  • Finding out why garbage collection is putting objects into gc.garbage.


  • An ObjectGraph class representing a collection of objects and references.
  • Computation of strongly connected components of the object graph.
  • Ability to export to JSON and reimport later for offline analysis.
  • Export of images via Graphviz.
  • Supports Python 2 and Python 3 (CPython only).


  • Currently requires Python version 2.7 or version >= 3.3. If there's any interest in Python 2.6 or Python 3.2 support let me know, and I may work on those. It's unlikely that versions earlier than 2.6 or 3.2 will ever be supported.
  • The export_image method for exporting a graph in image form requires Graphviz to be installed.
  • Uses the six package to support Python 2 and Python 3 from a single codebase.
  • Refcycle is CPython only.


Up-to-date documentation can be found on "Read the Docs", at

Installing refcycle

The latest release of refcycle is available from the Python Package Index, at On most systems, it can be installed in the usual way using easy_install or pip:

pip install -U refcycle

The currently-in-development version can be obtained from the project's GitHub homepage:


The refcycle package is copyright (c) 2013-2017 Mark Dickinson.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.