I want to add some methods to str class ,but when I change the __init__ methods I break into problems
class Uri(str): def __init__(self,*inputs): print inputs if len(inputs)>1: str.__init__(self,'<%s:%s>'%inputs[:2]) else: str.__init__(self,inputs[0]) print inputs a=Uri('ciao','gracco')
Traceback (most recent call last): File "prova.py", line 9, in ? a=Uri('ciao','gracco') TypeError: str() takes at most 1 argument (2 given)
where is the str() wrong call.I suppose It's the __new__ method which is wrong or me .Thanks for help
Strings are immutable, so you need to override __new__ rather than __init__.
Py> class Uri(str):
... def __new__(cls, *inputs):
... print inputs
... if len(inputs) > 1:
... self = str.__new__(cls, '<%s:%s>'% inputs[:2])
... else:
... self = str.__new__(cls, inputs[0])
... return self
...
Py> Uri('ciao', 'gracco')
('ciao', 'gracco')
'<ciao:gracco>'Note that the first argument is the class object rather than the new instance. The __new__ method *creates* the instance, and returns it.
See here for the gory details of overriding immutable types: http://www.python.org/doc/newstyle.html
Cheers, Nick.
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Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
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http://boredomandlaziness.skystorm.net
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