Can one get "for x in y" to work for non builtin classes?

[M.-A. Lemburg]

On 2008-03-02 15:06, Preben Randhol wrote:
> Hi
> 
> I'm making a kind of ordered dictionary class. It is not exactly a
> dictionary, but it uses a list and dictionary to store the data. 
> 
> Something like:
> 
> 	class dbase(list):
> 	'''Database class keeping track of the order and data'''
> 
> 	def __init__(self):
> 		self.__data = {}
> 		self.__order = []
> 		self.__uniq_id = 0
> 
> I'm just wondering if it is possible to get my class to work so that if
> one do:
> 
> 
> 	d=dbase()
> 	d.append("Data")
> 	d.append([1,2])
> 	
> one can do like this to iterate over the data.
> 
> 	for x in d:
> 		...
> 
> I'm looking at the list class but I don't quite understand from pydoc
> which __ __ methods I have to implement to get the above to work.

The easiest is to implement an iterator which then get's
returned by the .__iter__() method.

http://www.python.org/doc/lib/typeiter.html

It's also possible to implement .__getitem__() and .__len__()
methods and have Python create an iterator on-the-fly. That's
how Python used to work before iterators were added to the
language.

-- 
Marc-Andre Lemburg
eGenix.com

Professional Python Services directly from the Source  (#1, Mar 03 2008)
 >>> Python/Zope Consulting and Support ...        http://www.egenix.com/
 >>> mxODBC.Zope.Database.Adapter ...             http://zope.egenix.com/
 >>> mxODBC, mxDateTime, mxTextTools ...        http://python.egenix.com/
________________________________________________________________________

:::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,MacOSX for free ! ::::


    eGenix.com Software, Skills and Services GmbH  Pastor-Loeh-Str.48
     D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg
            Registered at Amtsgericht Duesseldorf: HRB 46611