有没有办法在 Python 中获取对象的当前引用计数？

Question

有没有办法在 Python 中获取对象的当前引用计数？

Answer 1

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.

Answer 2

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 .

Answer 3

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”, ie “clone if referenced elsewhere”.

Answer 4

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.

Answer 5

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)