New instance of a class : not reset?

[Jean-Francois]

Hi,

In the following example, I don't understand why attribute 'data' is
not reset when I get the new instance of Bag
It works if I make a copy (data[:]) but I want to understand why

Thanks


class Bag(object):
def __init__(self, data = []):
self.data = data
#self.data = data[:]
def add(self, x):
self.data.append(x)

bag = Bag()
print bag.data
bag.add('toto')
print bag.data
bag = Bag() # new instance of Bag, all attributes clear?
print bag.data # 'toto' is still there !!!

 

[MRAB]

Hi,

In the following example, I don't understand why attribute 'data' is
not reset when I get the new instance of Bag
It works if I make a copy (data[:]) but I want to understand why

Thanks


class Bag(object):
def __init__(self, data = []):
self.data = data
#self.data = data[:]
def add(self, x):
self.data.append(x)

bag = Bag()
print bag.data
bag.add('toto')
print bag.data
bag = Bag() # new instance of Bag, all attributes clear?
print bag.data # 'toto' is still there !!!

See:
http://effbot.org/zone/default-values.htm