The LSST data management science pipelines software consists of more than 100,000 lines of Python 2 code. LSST operations will begin after support for Python 2 has been dropped by the Python community in 2020, and we must therefore plan to migrate the codebase to Python 3. During the transition period we must also support our community of active Python 2 users and this complicates the porting significantly. We have decided to use the Python future package as the basis for our port to enable support for Python 2 and Python 3 simultaneously, whilst developing with a mindset more suited to Python 3. In this paper we report on the current status of the port and the difficulties that have been encountered.

翻译：LSST数据管理管道科学软件由10万多行的Python 2代码组成。LSST操作将在2020年Python社区放弃对Python 2的支持后开始,因此我们必须计划将代码库迁移到Python 3. 在过渡期间,我们还必须支持活跃的Python 2用户群体,这大大地使港口更复杂。我们决定使用Python 未来软件包作为我们的港口的基础,以便能够同时支持Python 2和Python 3,同时发展一种更适合Python 3的思维模式。我们在本文件中报告了港口的现状和遇到的困难。