Pympler is a development tool to measure, monitor and analyze the memory behavior of Python objects in a running Python application.

By pympling a Python application, detailed insight in the size and the lifetime of Python objects can be obtained. Undesirable or unexpected runtime behavior like memory bloat and other “pymples” can easily be identified.

Pympler integrates three previously separate modules into a single, comprehensive profiling tool. The asizeof module provides basic size information for one or several Python objects, module muppy is used for on-line monitoring of a Python application and module Class Tracker provides off-line analysis of the lifetime of selected Python objects.

A web profiling frontend exposes process statistics, garbage visualisation and class tracker statistics.


Pympler is written entirely in Python, with no dependencies to external libraries. It integrates Bottle and Highcharts. Pympler has been tested with Python 2.5, 2.6, 2.7, 3.1, 3.2, 3.3 and 3.4.

Pympler is platform independent and has been tested on various Linux distributions (32bit and 64bit), Windows 7 and MacOS X.


If you have pip installed, the easiest way to get Pympler is:

pip install pympler

Alternately, download Pympler releases from the Python Package Index or check out the latest development revision with git. Please see the README file for installation instructions.

Target Audience

Every Python developer interested in analyzing the memory consumption of their Python program should find a suitable, readily usable facility in Pympler.

Usage Examples

pympler.asizeof can be used to investigate how much memory certain Python objects consume. In contrast to sys.getsizeof, asizeof sizes objects recursively. You can use one of the asizeof functions to get the size of these objects and all associated referents:

>>> from pympler import asizeof
>>> obj = [1, 2, (3, 4), 'text']
>>> asizeof.asizeof(obj)
>>> print asizeof.asized(obj, detail=1).format()
[1, 2, (3, 4), 'text'] size=176 flat=48
    (3, 4) size=64 flat=32
    'text' size=32 flat=32
    1 size=16 flat=16
    2 size=16 flat=16

Memory leaks can be detected by using muppy. While the garbage collector debug output can report circular references this does not easily reveal where the leaks come from. Muppy can identify if objects are leaked out of a scope between two reference points:

>>> from pympler import tracker
>>> tr = tracker.SummaryTracker()
>>> function_without_side_effects()
>>> tr.print_diff()
  types |   # objects |   total size
======= | =========== | ============
   dict |           1 |    280     B
   list |           1 |    192     B

Tracking the lifetime of objects of certain classes can be achieved with the Class Tracker. This gives insight into instantiation patterns and helps to understand how specific objects contribute to the memory footprint over time:

>>> from pympler import classtracker
>>> tr = classtracker.ClassTracker()
>>> tr.track_class(Document)
>>> tr.create_snapshot()
>>> create_documents()
>>> tr.create_snapshot()
>>> tr.stats.print_summary()
              active      1.42 MB      average   pct
   Document     1000    195.38 KB    200     B   13%


Pympler was founded in August 2008 by Jean Brouwers, Ludwig Haehne, and Robert Schuppenies with the goal of providing a complete and stand-alone memory profiling solution for Python.

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