Browse files and subfolders in Python

You can use os.walk() to recursively iterate through a directory and all its subdirectories:

for root, dirs, files in os.walk(path):
    for name in files:
        if name.endswith((".html", ".htm")):
            # whatever

To build a list of these names, you can use a list comprehension:

htmlfiles = [os.path.join(root, name)
             for root, dirs, files in os.walk(path)
             for name in files
             if name.endswith((".html", ".htm"))]