CODEWITHSUNDEEP
pythonrefcounting
AJ
AJ

Reputation:

Is there a way to get the current ref count of an object in Python?

Is there a way to get the current ref count of an object in Python?

Upvotes: 141

Views: 64515

Answers (5)

Utkarsh
Utkarsh

Reputation: 645

Every object in Python has a reference count and a pointer to a type. We can get the current reference count of an object with the sys module. You can use sys.getrefcount(object), but keep in mind that passing in the object to getrefcount() increases the reference count by 1.

import sys

name = "Steve"

# 2 references, 1 from the name variable and 1 from getrefcount
sys.getrefcount(name)

Upvotes: 3

Gautam Vanama
Gautam Vanama

Reputation: 115

import ctypes

my_var = 'hello python'
my_var_address = id(my_var)

ctypes.c_long.from_address(my_var_address).value

ctypes takes address of the variable as an argument. The advantage of using ctypes over sys.getRefCount is that you need not subtract 1 from the result.

Upvotes: 9

Frank-Rene Schäfer
Frank-Rene Schäfer

Reputation: 3352

There is gc.get_referrers() and sys.getrefcount(). But, It is kind of hard to see how sys.getrefcount(X) could serve the purpose of traditional reference counting. Consider:

import sys

def function(X):
    sub_function(X)

def sub_function(X):
    sub_sub_function(X)

def sub_sub_function(X):
    print sys.getrefcount(X)

Then function(SomeObject) delivers '7',
sub_function(SomeObject) delivers '5',
sub_sub_function(SomeObject) delivers '3', and
sys.getrefcount(SomeObject) delivers '2'.

In other words: If you use sys.getrefcount() you must be aware of the function call depth. For gc.get_referrers() one might have to filter the list of referrers.

I would propose to do manual reference counting for purposes such as “isolation on change”, i.e. “clone if referenced elsewhere”.

Upvotes: 13

tehvan
tehvan

Reputation: 10369

According to the Python documentation, the sys module contains a function:

import sys
sys.getrefcount(object) #-- Returns the reference count of the object.

Generally 1 higher than you might expect, because of object arg temp reference.

Upvotes: 155

kquinn
kquinn

Reputation: 10740

Using the gc module, the interface to the garbage collector guts, you can call gc.get_referrers(foo) to get a list of everything referring to foo.

Hence, len(gc.get_referrers(foo)) will give you the length of that list: the number of referrers, which is what you're after.

See also the gc module documentation.

Upvotes: 86

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