def _find_project_dir(ftp, base_dir, projectid):
    """Find a genome project directory in ftp directory based upon directory name postfix. Return None if not found."""
    # Retrieve listing of directories under base_dir
    directory_listing = ftp.nlst(base_dir)

    # Find projectid dir based on directory suffix
    dir_suffix = '_uid{0}'.format(projectid)
    for ftp_file in directory_listing:
        if ftp_file.endswith(dir_suffix):
            return ftp_file
    return None