new class-instance is not getting initialized

[Erik Max Francis]

Axel Straschil wrote:

>         def __init__(self, flags=[]):
	...
>         def __init__(self, props={}):
	...
>         def __init__(self, tag, flags=[], props={}, Class=None):
	...
>         def __init__(self, tag, content=None, flags=[], props={},
> Class=None):
	...
>         def __init__(self, type=None, name=None, value=None,
> size=None, flags=[],

The problem is here.  In Python, default arguments are evaluated and
stowed away once, at definition time.  When those objects are mutable
(e.g., lists and dictionaries), that means that the mutable object is
shared by all callers:

>>> def f(x, l=[]):
...  l.append(x)
...  print l
... 
>>> f(1)
[1]
>>> f(2)
[1, 2]
>>> f(3)
[1, 2, 3]

Usually this isn't what you want (as in this case), so you should
protect the mutable objects with something like:

>>> def g(x, l=None):
...  if l is None:
...   l = [] # this way it'll be a unique object every time
...  l.append(x)
...  print l
... 
>>> g(1)
[1]
>>> g(2)
[2]
>>> g(3)
[3]


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