parser.py 文件源码

def parse_sub(self):
        lineno = self.stream.current.lineno
        left = self.parse_concat()
        while self.stream.current.type == 'sub':
            next(self.stream)
            right = self.parse_concat()
            left = nodes.Sub(left, right, lineno=lineno)
            lineno = self.stream.current.lineno
        return left