elements.py 文件源码

def _literal_as_text(element, warn=False):
    if isinstance(element, Visitable):
        return element
    elif hasattr(element, '__clause_element__'):
        return element.__clause_element__()
    elif isinstance(element, util.string_types):
        if warn:
            util.warn_limited(
                "Textual SQL expression %(expr)r should be "
                "explicitly declared as text(%(expr)r)",
                {"expr": util.ellipses_string(element)})

        return TextClause(util.text_type(element))
    elif isinstance(element, (util.NoneType, bool)):
        return _const_expr(element)
    else:
        raise exc.ArgumentError(
            "SQL expression object or string expected, got object of type %r "
            "instead" % type(element)
        )