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Size: 1273
Comment: __slots__ has to be defined at class level; defining it in __init__ doesn't work
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← Revision 7 as of 2008-11-15 14:00:59 ⇥
Size: 1328
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| Deletions are marked like this. | Additions are marked like this. |
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| class Msg( dict ): | class Msg(dict): |
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| def __init__( self, msg_type, kv_dict = {} ): dict.__init__( self ) self[ "msg-type" ] = msg_type self.update( kv_dict ) def Type( self ): return self[ "msg-type" ] def __getitem__( self, k ): return self.get( k, None ) def __delitem__( self, k ): if self.has_key( k ): dict.__delitem__( self, k ) def __str__( self ): pp = pprint.pformat( dict(self) ) return "%s: %s" % (self.Type(), pp ) |
def __init__(self, msg_type, kv_dict = {}): dict.__init__(self) self["msg-type"] = msg_type self.update(kv_dict) def Type(self): return self["msg-type"] def __getitem__(self, k): return self.get(k, None) def __delitem__(self, k): if self.has_key(k): dict.__delitem__(self, k) def __str__(self): pp = pprint.pformat(dict(self)) return "%s: %s" % (self.Type(), pp) |
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| ["Python-2.2"], SubclassingBuiltInTypes, UsingSlots | [[Python-2.2]], SubclassingBuiltInTypes, UsingSlots |
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| * Is this bad Python-2.2 code? Make improvements..! I ''do'' think it's worth showing how to use slots in the context of subclassing dict; In many cases, I think, people would want to do it. I ''do'' wonder if slots should be specified before or after the initializer- something to put on the UsingSlots page. -- LionKimbro [[DateTime(2003-09-07T17:07:24Z)]] | * Is this bad Python-2.2 code? Make improvements..! I ''do'' think it's worth showing how to use slots in the context of subclassing dict; In many cases, I think, people would want to do it. I ''do'' wonder if slots should be specified before or after the initializer- something to put on the UsingSlots page. -- LionKimbro <<DateTime(2003-09-07T17:07:24Z)>> [[lwickjr]]: Before, I think, collected with the other declaritives. |
Subclassing Dictionaries
The process differs by Python version.
Python-2.2
Derive from dict.
ex:
1 class Msg(dict):
2
3 __slots__ = [] # no attributes
4
5 def __init__(self, msg_type, kv_dict = {}):
6 dict.__init__(self)
7 self["msg-type"] = msg_type
8 self.update(kv_dict)
9
10 def Type(self):
11 return self["msg-type"]
12
13 def __getitem__(self, k):
14 return self.get(k, None)
15
16 def __delitem__(self, k):
17 if self.has_key(k):
18 dict.__delitem__(self, k)
19
20 def __str__(self):
21 pp = pprint.pformat(dict(self))
22 return "%s: %s" % (self.Type(), pp)
The __slots__ line indicates that Msg has no attributes of its own, preserving memory; see UsingSlots.
See Also
Python-2.2, SubclassingBuiltInTypes, UsingSlots
Questions
Is this bad Python-2.2 code? Make improvements..! I do think it's worth showing how to use slots in the context of subclassing dict; In many cases, I think, people would want to do it. I do wonder if slots should be specified before or after the initializer- something to put on the UsingSlots page. -- LionKimbro 2003-09-07 17:07:24 lwickjr: Before, I think, collected with the other declaritives.