Find files matching a specific file extension, via recursive search through input directory.

files_matching_file_extension.py

def find_filenames(input_directory, file_extension):
    """Return list of filenames matching file extension."""
    filelist = []
    for root, _, files in os.walk(input_directory):
        for file in files:
            if file.endswith(file_extension):
                filename = os.path.join(root, file)
                filelist.append(filename)
    return filelist