Create a list of all files in directory and subdirectories in python

Question

I would like to come up with the most optimal way of listing all files in a directory and its subdirectories. Once done, I would like to filter them down. So, optimally this would be done in 2 lines:

def getFilesContaining(filename):
    files = map(lambda x: os.path.join(x, file), os.walk('.')) #Note: this map does NOT work
    filtered_files = filter(lambda x: filename in x, files)
    return filtered_files 

Answer 1

def getFilesContaining(filename):
    paths = (os.path.join(root, f) for root, dirs, files in os.walk('.')
             for f in files) 
    return (path for path in paths if filename in path)

This returns an iterator. In your version, filter returns a list. If you really want a list, change the return value into a list comprehension by replacing the outer parentheses (...) into brackets [...] .