[Twirrim]

Use a linter. Most IDEs will do it for you natively, and even if you're dealing with a terminal based editor like vim, it's really easy to get the output of pylint, flake8 etc. running in it. It's extremely rare I ever get a syntax error make it through to code review, let alone build/deploy.

[baroffoos]

Linters catch the easy cases but when the problem spans multiple files they have no clue what is going on.

[ShinTakuya]

The mypy type linter performs type checking across files, in many cases even without explicit annotations.