newstr.py 文件源码

def join(self, iterable):
        errmsg = 'sequence item {0}: expected unicode string, found bytes'
        for i, item in enumerate(iterable):
            # Here we use type() rather than isinstance() because
            # __instancecheck__ is being overridden. E.g.
            # isinstance(b'abc', newbytes) is True on Py2.
            if isnewbytes(item):
                raise TypeError(errmsg.format(i))
        # Support use as a staticmethod: str.join('-', ['a', 'b'])
        if type(self) == newstr:
            return newstr(super(newstr, self).join(iterable))
        else:
            return newstr(super(newstr, newstr(self)).join(iterable))