objsize
The objsize
Python package allows for the exploration and
measurement of an object’s complete memory usage in bytes, including its
child objects. This process, often referred to as deep size calculation,
is achieved through Python’s internal Garbage Collection (GC) mechanism.
The objsize
package is designed to ignore shared objects, such as
None
, types, modules, classes, functions, and lambdas, because they
are shared across many instances. One of the key performance features of
objsize
is that it avoids recursive calls, ensuring a faster and
safer execution.
Key Features
Traverse objects’ subtree
Calculates the size of objects, including nested objects (deep size), in bytes
Exclude non-exclusive objects
Exclude specified objects subtree
Provides flexibility by allowing users to define custom handlers for:
Object’s size calculation
Object’s referents (i.e., its children)
Object filter (skip specific objects)
Documentation
Traversal over Python's objects subtree and calculating the total size of the subtree (deep size). |
Install
pip install objsize==0.7.0
Basic Usage
Calculate the size of the object including all its members in bytes.
>>> import objsize
>>> objsize.get_deep_size(dict(arg1='hello', arg2='world'))
340
It is possible to calculate the deep size of multiple objects by passing multiple arguments:
>>> objsize.get_deep_size(['hello', 'world'], dict(arg1='hello', arg2='world'), {'hello', 'world'})
628
Complex Data
objsize
can calculate the size of an object’s entire subtree in
bytes regardless of the type of objects in it, and its depth.
Here is a complex data structure, for example, that include a self reference:
my_data = list(range(3)), list(range(3, 6))
class MyClass:
def __init__(self, x, y):
self.x = x
self.y = y
self.d = {'x': x, 'y': y, 'self': self}
def __repr__(self):
return f"{self.__class__.__name__}()"
my_obj = MyClass(*my_data)
We can calculate my_obj
deep size, including its stored data.
>>> objsize.get_deep_size(my_obj)
724
We might want to ignore non-exclusive objects such as the ones stored in
my_data
.
>>> objsize.get_deep_size(my_obj, exclude=[my_data])
384
Or simply let objsize
detect that automatically:
>>> objsize.get_exclusive_deep_size(my_obj)
384
Special Cases
Some objects handle their data in a way that prevents Python’s GC from detecting it. The user can supply a special way to calculate the actual size of these objects.
Case 1: torch
Using a simple calculation of the object size won’t work for
torch.Tensor
.
>>> import torch
>>> objsize.get_deep_size(torch.rand(200))
72
So the user can define its own size calculation handler for such cases:
import objsize
import sys
import torch
def get_size_of_torch(o):
# `objsize.safe_is_instance` catches `ReferenceError` caused by `weakref` objects
if objsize.safe_is_instance(o, torch.Tensor):
return sys.getsizeof(o) + (o.element_size() * o.nelement())
else:
return sys.getsizeof(o)
Then use it as follows:
>>> objsize.get_deep_size(
... torch.rand(200),
... get_size_func=get_size_of_torch
... )
872
The above approach may neglect the object’s internal structure. The user
can help objsize
to find the object’s hidden storage by supplying it
with its own referent and filter functions:
import objsize
import gc
import torch
def get_referents_torch(*objs):
# Yield all native referents
yield from gc.get_referents(*objs)
for o in objs:
# If the object is a torch tensor, then also yield its storage
if type(o) == torch.Tensor:
yield o.untyped_storage()
# `torch.dtype` is a common object like Python's types.
MySharedObjects = (*objsize.SharedObjectOrFunctionType, torch.dtype)
def filter_func(o):
return not objsize.safe_is_instance(o, MySharedObjects)
Then use these as follows:
>>> objsize.get_deep_size(
... torch.rand(200),
... get_referents_func=get_referents_torch,
... filter_func=filter_func
... )
928
Case 2: weakref
Using a simple calculation of the object size won’t work for
weakref.proxy
.
>>> from collections import UserList
>>> o = UserList([0]*100)
>>> objsize.get_deep_size(o)
1032
>>> import weakref
>>> o_ref = weakref.proxy(o)
>>> objsize.get_deep_size(o_ref)
72
To mitigate this, you can provide a method that attempts to fetch the proxy’s referents:
import weakref
import gc
def get_weakref_referents(*objs):
yield from gc.get_referents(*objs)
for o in objs:
if type(o) in weakref.ProxyTypes:
try:
yield o.__repr__.__self__
except ReferenceError:
pass
Then use it as follows:
>>> objsize.get_deep_size(o_ref, get_referents_func=get_weakref_referents)
1104
After the referenced object will be collected, then the size of the proxy object will be reduced.
>>> del o
>>> gc.collect()
>>> # Wait for the object to be collected
>>> objsize.get_deep_size(o_ref, get_referents_func=get_weakref_referents)
72
Object Size Settings
To avoid repeating the input settings when handling the special cases
above, you can use the ObjSizeSettings
class.
>>> torch_objsize = objsize.ObjSizeSettings(
... get_referents_func=get_referents_torch,
... filter_func=filter_func,
... )
>>> torch_objsize.get_deep_size(torch.rand(200))
928
>>> torch_objsize.get_deep_size(torch.rand(300))
1328
See ObjSizeSettings
for the
list of configurable parameters.
Traversal
A user can implement its own function over the entire subtree using the traversal method, which traverses all the objects in the subtree.
>>> for o in objsize.traverse_bfs(my_obj):
... print(o)
...
MyClass()
{'x': [0, 1, 2], 'y': [3, 4, 5], 'd': {'x': [0, 1, 2], 'y': [3, 4, 5], 'self': MyClass()}}
[0, 1, 2]
[3, 4, 5]
{'x': [0, 1, 2], 'y': [3, 4, 5], 'self': MyClass()}
2
1
0
5
4
3
Similar to before, non-exclusive objects can be ignored.
>>> for o in objsize.traverse_exclusive_bfs(my_obj):
... print(o)
...
MyClass()
{'x': [0, 1, 2], 'y': [3, 4, 5], 'd': {'x': [0, 1, 2], 'y': [3, 4, 5], 'self': MyClass()}}
{'x': [0, 1, 2], 'y': [3, 4, 5], 'self': MyClass()}
Alternative
Pympler also supports
determining an object deep size via pympler.asizeof()
. There are two
main differences between objsize
and pympler
.
objsize
has additional features:Traversing the object subtree: iterating all the object’s descendants one by one.
Excluding non-exclusive objects. That is, objects that are also referenced from somewhere else in the program. This is true for calculating the object’s deep size and for traversing its descendants.
objsize
has a simple and robust implementation with significantly fewer lines of code, compared topympler
. The Pympler implementation uses recursion, and thus have to use a maximal depth argument to avoid reaching Python’s max depth.objsize
, however, uses BFS which is more efficient and simple to follow. Moreover, the Pympler implementation carefully takes care of any object type.objsize
archives the same goal with a simple and generic implementation, which has fewer lines of code.
License: BSD-3
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