def where(boolean_expr, true_expr, false_null_expr):
    """
    Equivalent to the ternary expression: if X then Y else Z

    Parameters
    ----------
    boolean_expr : BooleanValue (array or scalar)
    true_expr : value
      Values for each True value
    false_null_expr : value
      Values for False or NULL values

    Returns
    -------
    result : arity depending on inputs
      Type of true_expr used to determine output type
    """
    op = ops.Where(boolean_expr, true_expr, false_null_expr)
    return op.to_expr()