for iteration

Franck Bui-Huu Franck.BUI-HUU at
Mon Aug 25 10:26:46 CEST 2003

Thanks for your example but I haven't found __iter__ method in list type:

 >>> dir(list)
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', 
ce__', '__doc__', '__eq__', '__ge__', '__getattribute__', '__getitem__', 
lice__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', 
'__le__', '__
len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', 
'__repr__', '__r
mul__', '__setattr__', '__setitem__', '__setslice__', '__str__', 
'append', 'coun
t', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

Do you know why ?

Peter Otten a écrit:

>Franck Bui-Huu wrote:
>>I'm trying to customize a list by overriding __getitem__ method but
>>this change seems to not work with for iteration.
>>When I use my customized list in a for iteration, all changes made
>>in __getitem__ are not take into account.
>>How can I modify this behaviour ?
>For the for loop to work properly, you have to overide the __iter__()
>method, e.g.:
>class MyList(list):
>    def __getitem__(self, index):
>        """ for the sake of this example convert item to uppercase """
>        return list.__getitem__(self, index).upper()
>    def __iter__(self):
>        """ implemented using a generator """
>        for i in range(len(self)):
>            yield self[i] # calls the customized __getitem__()
>myList = MyList(["alpha", "beta", "gamma"])
># works with __getitem__()
>for index in range(len(myList)):
>    print myList[index]
># works with __iter__()
>for item in myList:
>    print item

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