I hesitate to post this because I'm out of my depth - I've never used
generators before, and I'm not 100% certain that this strange compromise
between imperative (the usual breadth/depth switch using queues) and a
functional (the usual pre/post switch using the call stack) algorithms is
ok. However, it appears to work and may be useful - it's a simple
extension to Noah's code that allows the user to choose between breadth-
and depth-first traversal. It is more expensive, using a list as either
fifo or lifo queue (depending on breadth/depth selection).
[Noah - I decided to post this rather than bother you again - hope that's OK]
#!/usr/bin/python2.2
from __future__ import generators # needed for Python 2.2
import os
def walktree(basepath=".", postorder=True, depthfirst=True,
ignorelinks=True):
"""Noah Spurrier's code, modified to allow depth/breadth-first
traversal. The recursion is there *only* to allow postorder
processing as the stack rolls back - the rest of the algorithm is
imperative and queue would be declared outside helper if I knew
how."""
def helper(queue):
if queue:
if depthfirst: dir = queue.pop(-1)
else: dir = queue.pop(0)
children = os.listdir(dir)
dirs, nondirs = [], []
for name in children:
fullpath = os.path.join(dir, name)
if os.path.isdir(fullpath) and not \
(ignorelinks and os.path.islink(fullpath)):
dirs.append(name)
queue.append(fullpath)
else:
nondirs.append(name)
if not postorder:
yield dir, dirs, nondirs
for rest in helper(queue):
yield rest
if postorder:
yield dir, dirs, nondirs
return helper([basepath])
def test():
for basepath, dirs, nondirs in \
walktree(postorder=True, depthfirst=False):
for name in dirs:
print os.path.join(basepath, name)
for name in nondirs:
print os.path.join(basepath, name)
if __name__ == '__main__':
test()
--
http://www.acooke.org/andrew
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