expressions.py 文件源码

def __init__(self, *expressions, **extra):
        if self.arity is not None and len(expressions) != self.arity:
            raise TypeError(
                "'%s' takes exactly %s %s (%s given)" % (
                    self.__class__.__name__,
                    self.arity,
                    "argument" if self.arity == 1 else "arguments",
                    len(expressions),
                )
            )
        output_field = extra.pop('output_field', None)
        super(Func, self).__init__(output_field=output_field)
        self.source_expressions = self._parse_expressions(*expressions)
        self.extra = extra