Hello,
Python 3.5 is not supported upstream, neither by the CPython development team nor by third-party projects such as NumPy. Our CI for Python 3.5 has just started failing because a dependency of pytest doesn't support it anymore: https://github.com/apache/arrow/runs/1458449054?check_suite_focus=true Unless someone objects very strongly (and pledges to provide the required maintenance effort), it seems we finally need to drop Python 3.5 support before we release Arrow 3.0.0. See also https://issues.apache.org/jira/browse/ARROW-5679 Regards Antoine.