expression.py 文件源码

def literal_column(text, type_=None):
    """Return a textual column expression, as would be in the columns
    clause of a ``SELECT`` statement.

    The object returned supports further expressions in the same way as any
    other column object, including comparison, math and string operations.
    The type\_ parameter is important to determine proper expression behavior
    (such as, '+' means string concatenation or numerical addition based on
    the type).

    :param text: the text of the expression; can be any SQL expression.
      Quoting rules will not be applied. To specify a column-name expression
      which should be subject to quoting rules, use the :func:`column`
      function.

    :param type\_: an optional :class:`~sqlalchemy.types.TypeEngine`
      object which will
      provide result-set translation and additional expression semantics for
      this column. If left as None the type will be NullType.

    """
    return ColumnClause(text, type_=type_, is_literal=True)