Here is a simple but powerful way to use Python to search and find all files with a specific extension within a given folder and all of its sub-folders using os.walk(). I use it a lot to find map documents with broken data sources, images that need to be organized or just to get a quick count of certain files in a directory.
directorypath = raw_input("Enter a directory path: ")
extension = raw_input("enter an extension: .")
#Loop through all folders and subfolders in your target directory.
for root, dirs, files in os.walk(directorypath):
fileList = [os.path.join(root, f) for f in files if f.endswith(extension)]
for item in fileList:
print item #or do something else with each file found.