def snapPath(basePath, snapNum, chunkNum=0):
    """
    Return path to a chunk file of snapshot.

    Args:
        basePath (str): Base path of the simulation data. This path usually 
            ends with "output".
        snapNum (int): Number of the snapshot.
        chunkNum (int, default to 0): Number of the chunk.

    Returns:
        str: Path to a chunk file.
    """

    snapPath = basePath + "/snapdir_%03d/"%(snapNum)
    filePath = snapPath + "snap_%03d.%d.hdf5"%(snapNum, chunkNum)

    return filePath