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Title: Recursive generators
Author: Sandro Tosi
Last modified: 2007-08-26
Since I've lost a couple of days on this problem, I'm going to
describe how to write recursive generator functions.
The problem I needed to solve was to recursive find pdf files in a
directory tree.
Coming back to my previous programming languages knowledge, I've
started writing this code:
def find_pdf_files_in_dir_recursive(directory):
for path in directory.split(os.pathsep):
# check first in the dir passed as parameter
for found_file in glob.glob(os.path.join(path, "*.pdf")):
yield found_file
# dircache output is sorted and cached
for item in dircache.listdir(path):
# if it's a dir, then go recursive on it
if os.path.isdir(path+"/"+item):
find_pdf_files_in_dir_recursive(path+"/"+item)
but with it, I received only the files in the first directory, the one
passed as generator parameter, and no result from the rest of the
tree.
The solution is: LOOP OVER RECURSIVE CALL! It's sort of
counterintuitive to me, but that's it:
def find_pdf_files_in_dir_recursive(directory):
for path in directory.split(os.pathsep):
# check first in the dir passed as parameter
for match in glob.glob(os.path.join(path, "*.pdf")):
yield match
# dircache output is sorted and cached
# let's join path and item, since files list
# returned from listdir has path stripped off
for subpath in [os.path.join(path, item) for item in dircache.listdir(path)]:
# if it's a dir, then go recursive on it
if os.path.isdir(subpath):
# yield every item found in the recursive call!
for subfile in find_pdf_files_in_dir_recursive(subpath):
yield subfile
And there you have your recursive generator.