Check files in current directory

How can I tell python to scan the current directory for a file called "filenames.txt" and if that file isn't there, 开发者_开发问答to extract it from a zip file called "files.zip"? I know how to work zipfile, I just don't know how to scan the current directory for that file and use if/then loops with it..

import os.path
try:    
    os.path.isFile(fname)
    # play with the file
except:
    # unzip file

import os, zipfile
if 'filenames.txt' in os.listdir('.'):
    print 'file is in current dir'
else:
    zf = zipfile.ZipFile('files.zip')
    zf.extract('filenames.txt')

From the documentation

$ pydoc os.path.exists
Help on function exists in os.path:

os.path.exists = exists(path)
    Test whether a path exists.  Returns False for broken symbolic links