Question

I am new to Python, and noticed something I believe its a bug.

Edit 2011-09-30:
Forget it. Now I know the attributes created are static and shared between the instances.
Hope this thread helps another python newbies in the same situation as mine.

Consider the following code:

class test():

    dictionary1 = {}
    list1 = []

    def method1(self):
        self.dictionary1.update({'1': 'unique entry'})
        self.list1 = ['unique list entry']

t=test()

print 'dictionary1 value:', t.dictionary1
print 'list1 value:', t.list1
t.method1()
print 'dictionary1 new value:', t.dictionary1
print 'list1 new value:', t.list1

t2=test()
print 'dictionary1 value:', t2.dictionary1, " -- error -- I just instantiated the class. The correct value would be {}"
print 'list1 value:', t.list1
t2.method1()
print 'dictionary1 new value:', t.dictionary1
print 'list1 new value:', t.list1

Now the question:

Why in line 19 the executed code shows: {'1': 'unique entry'}. I belive it would be: {}
Note that the list has the correct value: [] (empty list in line 20)

Using Python 2.6.6 (r266:84292, Sep 15 2010, 15:52:39) 
[GCC 4.4.5] on linux2

Sorry not so good english. From Brazil.

Edit 2011-09-30:
Forget it. Now I know the attributes created are static and shared between the instances.
Hope this thread helps another python newbies in the same situation as mine.

Answer 1

All your instances of test class share the same dictionary and list. The correct way to initialize the members would be:

class Test():
    def __init__(self):
        self.dictionary1 = {}
        self.list1 = []

Attributes assigned directly in the class body will be evaluated once and then shared between all instances. Since the __init__ method is run once per instance, a new list and dictionary will be created for each instance.