[Tutor] recursive generator

spir denis.spir at gmail.com
Sun Mar 7 13:58:05 CET 2010


Is it possible at all to have a recursive generator? I think at a iterator for a recursive data structure (here, a trie). The following code does not work: it only yields a single value. Like if child.__iter__() were never called.

    def __iter__(self):
        ''' Iteration on (key,value) pairs. '''
        print '*',
        if self.holdsEntry:
            yield (self.key,self.value)
        for child in self.children:
            print "<",
            print ">",
        raise StopIteration

With the debug prints in code above, "for e in t: print e" outputs:

* ('', 0)
< > < > < > < > < > < > < > < >

print len(t.children) # --> 9

Why is no child.__iter__() executed at all? I imagine this can be caused by the special feature of a generator recording current execution point. (But then, is it at all possible to have a call in a generator? Or does the issue only appear whan the callee is a generator itself?) Else, the must be an obvious error in my code.


la vita e estrany


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