bug in classlevel variabels

[thomasda]

BPO	1549499
Nosy	@birkenfeld

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2006-08-30.19:28:23.000>
created_at = <Date 2006-08-30.18:44:30.000>
labels = ['interpreter-core', 'invalid']
title = 'bug in classlevel variabels'
updated_at = <Date 2006-08-30.19:28:23.000>
user = 'https://bugs.python.org/thomasda'

bugs.python.org fields:

activity = <Date 2006-08-30.19:28:23.000>
actor = 'georg.brandl'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2006-08-30.18:44:30.000>
creator = 'thomasda'
dependencies = []
files = []
hgrepos = []
issue_num = 1549499
keywords = []
message_count = 2.0
messages = ['29711', '29712']
nosy_count = 2.0
nosy_names = ['georg.brandl', 'thomasda']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1549499'
versions = ['Python 2.4']

[thomasda]

class A:
    js = []
    
    def add (self, j):
        self.js.append(j)

    def clone (self):
        c = A()
        for j in self.js:
            c.add(j)
        return c

a = A()
b = a.clone()
b.add(3)

print a.js
print b.js

The above code should print "[]\n[3]", but instead it
prints "[3]\n[3]"!

It works as expected, if you change "js = []" to "def
__init__ (self):
self.js = []"

[birkenfeld]

Logged In: YES
user_id=849994

This is not a bug. The "js" list exists in the class's
namespace and exists only once, and if you don't rebind the
name, "self.js" always refers to this. Therefore it is
shared between instances.