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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Mon, 9 Jan 2012 16:20:32 -0700
Subject: Re: classes and __iter__
To: "david.garvey@gmail.com" <david.garvey@gmail.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:18717

On Mon, Jan 9, 2012 at 3:51 PM, david.garvey@gmail.com
<david.garvey@gmail.com> wrote:
> ...=A0=A0=A0=A0 def __iter__(self):
> ...=A0=A0=A0=A0=A0=A0=A0=A0 return iter(self.keylist, self.d)

This method is incorrect.  The 2-argument form of iter() is very
different from the 1-argument form.  Whereas the 1-argument form takes
an iterable, the 2-argument form takes a callable and a sentinel
value.  In that case, iter() attempts to call the callable until the
sentinel is returned.  In your code, it would attempt to call the
keylist (which would fail with a TypeError) until it returned the
dictionary as a result.  This would be more in line with what you're
trying to do:

def __iter__(self):
    for key in self.keylist:
        yield key, self.d[key]


>>>> for key in helo.keylist:
> ...=A0=A0=A0=A0 print "Key:%s Value:%s" %(key,helo.d[key])

Note that this works because you're not actually using the class's
__iter__ method here.  You're iterating over the keylist directly, not
over the containing class instance.