gcutils - Garbage collecting tools

The Python Garbage Collector (GC) doesn’t usually get too much attention, probably because:

  • Python’s reference counting effectively handles the vast majority of unused objects
  • People are slowly learning to avoid implementing object.__del__()
  • The collection itself strikes a good balance between simplicity and power (tunable generation sizes)
  • The collector itself is fast and rarely the cause of long pauses associated with GC in other runtimes

Even so, for many applications, the time will come when the developer will need to track down:

  • Circular references
  • Misbehaving objects (locks, __del__())
  • Memory leaks
  • Or just ways to shave off a couple percent of execution time

Thanks to the gc module, the GC is a well-instrumented entry point for exactly these tasks, and gcutils aims to facilitate it further.

boltons.gcutils.get_all(type_obj, include_subtypes=True)[source]

Get a list containing all instances of a given type. This will work for the vast majority of types out there.

>>> class Ratking(object): pass
>>> wiki, hak, sport = Ratking(), Ratking(), Ratking()
>>> len(get_all(Ratking))

However, there are some exceptions. For example, get_all(bool) returns an empty list because True and False are themselves built-in and not tracked.

>>> get_all(bool)

Still, it’s not hard to see how this functionality can be used to find all instances of a leaking type and track them down further using gc.get_referrers() and gc.get_referents().

get_all() is optimized such that getting instances of user-created types is quite fast. Setting include_subtypes to False will further increase performance in cases where instances of subtypes aren’t required.


There are no guarantees about the state of objects returned by get_all(), especially in concurrent environments. For instance, it is possible for an object to be in the middle of executing its __init__() and be only partially constructed.

class boltons.gcutils.GCToggler(postcollect=False)[source]

The GCToggler is a context-manager that allows one to safely take more control of your garbage collection schedule. Anecdotal experience says certain object-creation-heavy tasks see speedups of around 10% by simply doing one explicit collection at the very end, especially if most of the objects will stay resident.

Two GCTogglers are already present in the gcutils module:

  • toggle_gc simply turns off GC at context entrance, and re-enables at exit
  • toggle_gc_postcollect does the same, but triggers an explicit collection after re-enabling.
>>> with toggle_gc:
...     x = [object() for i in range(1000)]

Between those two instances, the GCToggler type probably won’t be used much directly, but is documented for inheritance purposes.

boltons.gcutils.toggle_gc = <boltons.gcutils.GCToggler object>

A context manager for disabling GC for a code block. See GCToggler for more details.

boltons.gcutils.toggle_gc_postcollect = <boltons.gcutils.GCToggler object>

A context manager for disabling GC for a code block, and collecting before re-enabling. See GCToggler for more details.