Are generators in nested functions possible?

Bjorn Pettersen BPettersen at NAREX.com
Fri Jun 21 01:13:10 CEST 2002


I've got the following code to generate the indicies of all nearest
neighbours (span levels) in a multi dimensional qube:

def generateIndexes(length=5, span=1):
    spanvalues = range(-span, span+1)
    
    def genInd(res, length):
        if length == 1:
            for val in spanvalues:
                yield res + [val]
        else:
            for i in range(length):
                for val in spanvalues:
                    genInd(res + [val], length-1)
    
    return genInd([], length)

However, when I try to use it it doesn't seem to return anything:

  >>> for i in generateIndexes(3):
  ...   print i
  ...
  >>>

I tried getting the iterator (or is it generator?) directly and calling
next() on it, and it seems like it raises a StopIteration exception
immediately:

  >>> g = generateIndexes(3)
  >>> g.next()
  Traceback (most recent call last):
    File "<stdin>", line 1, in ?
  StopIteration
  >>>

Can anyone help me understand what is going on here?

-- bjorn





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