URL tree walkers, recursive and non-recursive.

walk_url_tree.py

def walk_url_tree(urls):
    """
    Generator to walk a tree consisting of RegexURLPattern (with callback)
    and RegexURLResolver (with nested url_patterns).

    Recursive depth-first.
    """
    for u in urls:
        if hasattr(u, 'url_patterns'):
            for u2 in walk_url_tree(u.url_patterns):
                yield u2
        else:
            yield u

def walk_url_tree(urls):
    """
    Generator to walk a tree consisting of RegexURLPattern (with callback)
    and RegexURLResolver (with nested url_patterns).

    Non-recursive breadth-first.
    """
    ulist = list(urls)
    for u in ulist:
        try:
            ulist.extend(u.url_patterns)
        except AttributeError:
            yield u

def walk_url_tree(urls):
    """
    Generator to walk a tree consisting of RegexURLPattern (with callback)
    and RegexURLResolver (with nested url_patterns).

    Non-recursive depth-first in reverse, using a LIFO to avoid
    accumulating the entire list.
    """
    lifo = list(urls)
    while lifo:
        u = lifo.pop()
        try:
            lifo.extend(u.url_patterns)
        except AttributeError:
            yield u

def walk_url_tree(urls):
    """
    Generator to walk a tree consisting of RegexURLPattern (with callback)
    and RegexURLResolver (with nested url_patterns).

    Non-recursive breadth-first using chain_plus.
    """
    it = chain_plus(urls)
    for u in it:
        try:
            it.link(u.url_patterns)
        except AttributeError:
            yield u


from collections import deque

class chain_plus(object):
    """
    Same as itertools.chain() except this can be extended during iteration
    by linking more iterables to the end of the chain.
    """
    def __init__(self, *iterables):
        self._iterators = deque()
        self.link(*iterables)

    def __iter__(self):
        return self

    def link(self, *iterables):
        self._iterators.extend(iter(i) for i in iterables)

    def next(self):
        while self._iterators:
            try:
                return next(self._iterators[0])
            except StopIteration:
                self._iterators.popleft()
        raise StopIteration