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11.5. TaxonPhotoSet.walk(): Walk the tree

This method recursively walks the tree, yielding the current node, followed by its subtrees.

# - - -   T a x o n P h o t o S e t . w a l k

    def walk(self):
        '''Recursive tree walker, yielding nodes in pre-order.

The current node is generated first.

        #-- 1
        yield self

This method specifies that the children are generated in taxonomic order. Since the keys in the self._childMap dictionary are in phylogenetic order, we extract the key set, sort it, and then recursively generate the subtrees in order by that set.

        #-- 2
        # [ childKeys  :=  a list containing the keys of
        #                  self._childMap in ascendind order ]
        childKeys = self._childMap.keys()

        #-- 3
        # [ childKeys is a list of keys in self._childMap ->
        #     generate the nodes from subtrees rooted in the nodes
        #     that are values of self._childMap, in childKeys order ]
        for txKey in childKeys:
            childNode = self._childMap[txKey]
            for node in childNode.walk():
                yield node