Find out how much memory is being used by an object in Python [duplicate]

Question

How would you go about finding out how much memory is being used by an object? I know it is possible to find out how much is used by a block of code, but not by an instantiated object (anytime during its life), which is what I want.

Pudency

objgraph looks interesting: mg.pov.lt/objgraph – Drivel

Similar: stackoverflow.com/questions/449560/… – Eurythmics

Another approach is to use pickle. See this answer to a duplicate of this question. – Arlana

Graphical Test: https://mcmap.net/q/18867/-data-size-in-memory-vs-on-disk – Multipara

If it's an object of your class, you can be outgoing towards your users, and implement __sizeof__(self) for them. For example NumPy does that, and a.__sizeof__() is somewhat bigger (includes the object overhead), than a.nbytes - which is the number of bytes in the allocated array. – Godric

Answer 1

There's no easy way to find out the memory size of a python object. One of the problems you may find is that Python objects - like lists and dicts - may have references to other python objects (in this case, what would your size be? The size containing the size of each object or not?). There are some pointers overhead and internal structures related to object types and garbage collection. Finally, some python objects have non-obvious behaviors. For instance, lists reserve space for more objects than they have, most of the time; dicts are even more complicated since they can operate in different ways (they have a different implementation for small number of keys and sometimes they over allocate entries).

There is a big chunk of code (and an updated big chunk of code) out there to try to best approximate the size of a python object in memory.

You may also want to check some old description about PyObject (the internal C struct that represents virtually all python objects).

Doall

@culix: Seems like that again is now used in the Pympler module. – Publius

What if your object is pretty simple, such as a dict with an Int -> (Int, Int) mapping? In theory, calculating the size of such an object should be simple, right? – Viborg

If a book has references, to other books, its size didn't increase. – Vizier

Answer 2

Try this:

sys.getsizeof(object)

getsizeof() Return the size of an object in bytes. It calls the object’s __sizeof__ method and adds an additional garbage collector overhead if the object is managed by the garbage collector.

A recursive recipe

Cognate

Does this sys.getsizeof(object) return value includes the real object size instead of their pointer's size as fserb said above? – Warty

No, it will return the size of the pointer. – Chinaware

What's the difference between this and object.__sizeof__()? It seems that sys.getsizeof(object) returns a slightly larger value. EDIT: The latter also includes the garbage collector overhead. – Larder

I've found that sys.getsizeof(object.copy) often gives the correct value, where sys.getsizeof(object) gives you some far lower value (I guess the pointer size). – Ihab

don't forget import sys! – Familiar

It is not right. I created a pytorch tensor in CPU and its shape is (100000000,), sys.getsizeof(x.copy) shows 80. But the data type is float64. – Godwit

Yeah, I'm getting something way to small as well, this is not a great solution... I'm trying to figure out how large a machine learning model is in memory because it's taking up too much memory when I try to load it. There are like tens of thousands of rows of data in this object... so it's definitely larger than the 80 bytes I'm getting back. – Physiognomy

Answer 3

I haven't any personal experience with either of the following, but a simple search for a "Python [memory] profiler" yield:

• PySizer, "a memory profiler for Python," found at http://pysizer.8325.org/. However the page seems to indicate that the project hasn't been updated for a while, and refers to...

• Heapy, "support[ing] debugging and optimization regarding memory related issues in Python programs," found at http://guppy-pe.sourceforge.net/#Heapy.

Hope that helps.

Augmentation

Both for Python2, unfortunately – Degeneration

Answer 4

This must be used with care because an override on the objects __sizeof__ might be misleading.

Using the bregman.suite, some tests with sys.getsizeof output a copy of an array object (data) in an object instance as being bigger than the object itself (mfcc).

>>> mfcc = MelFrequencyCepstrum(filepath, params)
>>> data = mfcc.X[:]
>>> sys.getsizeof(mfcc)
64
>>> sys.getsizeof(mfcc.X)
>>>80
>>> sys.getsizeof(data)
80
>>> mfcc
<bregman.features.MelFrequencyCepstrum object at 0x104ad3e90>

Reddick

Answer 5

For big objects you may use a somewhat crude but effective method: check how much memory your Python process occupies in the system, then delete the object and compare.

This method has many drawbacks but it will give you a very fast estimate for very big objects.

Parcae

This is unlikely to be effective. Memory freed in a process does not have to be returned to the operating system, so looking for a decrease in memory use may not be accurate. – Fulguration

A similar approach of measuring python process resource usage before the object is created and after would be quite effective. – Nocturnal

Don't think so @AntonyHatchkins as python memory manager do not necessarily get new memory from the operating systems. To some extent, memory pool is kept allocated even if not in use, so when there's a new request, it may be fulfilled without the need to request more memory from the operating system. In other words, this approach is unreliable for both creation and destruction of objects. – Stanhope