Question

If I create a list in a python function and return it to the caller, how does garbage collection work on that list? Do I have to do anything to keep a memory leak from occurring?

For example:

#!/usr/bin/python

import random

class Example:
    def f1(self):
        list = []
        len = random.randint(0, 30)
        for i in range (0, len):
                list.append(random.randint(0, 65536))
        return list


random.seed(None)

e = Example()
while (1):
    l = e.f1()

Will this cause a memory leak? Does the ‘list’ in f1() have an appropriate reference count at all times? Does the caller of f1() have to do anything to keep a memory leak from occurring? Should the caller do a del() on the list or something?

Answer 1

There’s no memory leak here. The list assigned to l is the same list that is generated in the function. Python passes objects, not references or values.

Python keeps track of the references to that list: on each iteration of the while loop, a new list is created and assigned to l. This causes the previous one to no longer have any references, so it will be deleted.