若不包含子目录的遍历：
import glob
for filename in glob.glob("/data/testdata/*.jpg"):
print filename
包含子目录
import os
import fnmatch
def iterfindfiles(path, fnexp):
for root, dirs, files in os.walk(path):
for filename in fnmatch.filter(files, fnexp):
yield os.path.join(root, filename)
for filename in iterfindfiles(r"/data/testdata", "*.jpg"):
print filename
yield 用法讲解 http://www.ibm.com/developerworks/cn/opensource/os-cn-python-yield/