def PDB_ID(input_file, skip_lines=1):
    """input_file: file with PDB entry list
    skip_lines: lines to skip(defualt=1, column name)
    returns pdb list"""
    pdb_ids = open(input_file)
    lines=pdb_ids.readlines()[skip_lines:]
    strip_pdb_ids = [line.lower().strip() for line in lines if not line.strip().startswith("#")]

    pdb_ids.close()

    return strip_pdb_ids