def reverse_geometric_key(gkey):
    """Reverse a geometric key string into xyz coordinates.

    Parameters
    ----------
    gkey : str
        A geometric key.

    Returns
    -------
    list of float
        A list of XYZ coordinates.

    Examples
    --------
    >>> from math import pi
    >>> xyz = [pi, pi, pi]
    >>> gkey = geometric_key(xyz)
    >>> reverse_geometric_key(gkey)
    [3.142, 3.142, 3.142]
    """
    xyz = gkey.split(',')
    return [float(i) for i in xyz]