Memory leak when you create alias methods once the class has been instantiated.

output.txt

[3/5.0.2]niwi@localhost:~/tmp-memory-leak> python3 simple-test.py
Memory leak:
KK.__init__ 139987115392208
Foo.__init__ 139987115392016

No memory leak:
KK.__init__ 139987115392400
Bar__init__ 139987115392272
Bar.__del__ 139987115392272
KK.__del__ 139987115392400

Loop Foo:
KK.__init__ 139987115392400
Foo.__init__ 139987115392272
KK.__init__ 139987115392528
Foo.__init__ 139987115392464
KK.__init__ 139987115392656
Foo.__init__ 139987115392592
KK.__init__ 139987115392784
Foo.__init__ 139987115392720
KK.__init__ 139987115392912
Foo.__init__ 139987115392848

Loop Bar:
KK.__init__ 139987115393104
Bar__init__ 139987115392976
KK.__init__ 139987115393232
Bar__init__ 139987115393168
Bar.__del__ 139987115392976
KK.__del__ 139987115393104
KK.__init__ 139987115393104
Bar__init__ 139987115392976
Bar.__del__ 139987115393168
KK.__del__ 139987115393232
KK.__init__ 139987115393232
Bar__init__ 139987115393168
Bar.__del__ 139987115392976
KK.__del__ 139987115393104
KK.__init__ 139987115393104
Bar__init__ 139987115392976
Bar.__del__ 139987115393168
KK.__del__ 139987115393232
Bar.__del__ 139987115392976
KK.__del__ 139987115393104

[3/5.0.2]niwi@localhost:~/tmp-memory-leak> python2 simple-test.py
Memory leak:
KK.__init__ 140281337651984
Foo.__init__ 140281337651920

No memory leak:
KK.__init__ 140281337652176
Bar__init__ 140281337652112
Bar.__del__ 140281337652112
KK.__del__ 140281337652176

Loop Foo:
KK.__init__ 140281337652240
Foo.__init__ 140281337652176
KK.__init__ 140281337652368
Foo.__init__ 140281337652304
KK.__init__ 140281337652496
Foo.__init__ 140281337652432
KK.__init__ 140281337652624
Foo.__init__ 140281337652560
KK.__init__ 140281337652752
Foo.__init__ 140281337652688

Loop Bar:
KK.__init__ 140281337652880
Bar__init__ 140281337652816
KK.__init__ 140281337653008
Bar__init__ 140281337652944
Bar.__del__ 140281337652816
KK.__del__ 140281337652880
KK.__init__ 140281337652880
Bar__init__ 140281337652816
Bar.__del__ 140281337652944
KK.__del__ 140281337653008
KK.__init__ 140281337653008
Bar__init__ 140281337652944
Bar.__del__ 140281337652816
KK.__del__ 140281337652880
KK.__init__ 140281337652880
Bar__init__ 140281337652816
Bar.__del__ 140281337652944
KK.__del__ 140281337653008
Bar.__del__ 140281337652816
KK.__del__ 140281337652880

simple-test.py

# -*- coding: utf-8 -*-
from __future__ import print_function

class KK(object):
    def __init__(self):
        print("KK.__init__", id(self))

    def __del__(self):
        print("KK.__del__", id(self))

class Foo(object):
    def __init__(self):
        self.echo_bar = self.echo_foo
        self.kk = KK()
        print("Foo.__init__", id(self))

    def echo_foo(self):
        print("Foo")

    def __del__(self):
        print("Foo.__del__", id(self))

class Bar(object):
    def __init__(self):
        self.kk = KK()
        print("Bar__init__", id(self))

    def echo_foo(self):
        print("Fooo")

    def __del__(self):
        print("Bar.__del__", id(self))

if __name__ == "__main__":
    print("Memory leak:")
    foo = Foo()
    foo = None

    print("\nNo memory leak:")
    bar = Bar()
    bar = None

    print("\nLoop Foo:")
    for x in range(5):
        f = Foo()

    print("\nLoop Bar:")
    for x in range(5):
        b = Bar()