ops.py 文件源码

def reverse(self):

        kw = self.kw.copy()
        kw['existing_type'] = self.existing_type
        kw['existing_nullable'] = self.existing_nullable
        kw['existing_server_default'] = self.existing_server_default
        if self.modify_type is not None:
            kw['modify_type'] = self.modify_type
        if self.modify_nullable is not None:
            kw['modify_nullable'] = self.modify_nullable
        if self.modify_server_default is not False:
            kw['modify_server_default'] = self.modify_server_default

        # TODO: make this a little simpler
        all_keys = set(m.group(1) for m in [
            re.match(r'^(?:existing_|modify_)(.+)$', k)
            for k in kw
        ] if m)

        for k in all_keys:
            if 'modify_%s' % k in kw:
                swap = kw['existing_%s' % k]
                kw['existing_%s' % k] = kw['modify_%s' % k]
                kw['modify_%s' % k] = swap

        return self.__class__(
            self.table_name, self.column_name, schema=self.schema,
            **kw
        )