IDE's are used for more than just building the code; they provide UIs for debugging capabilities, code completion, syntax highlighting, refactoring support, VCS

IDE's are used for more than just building the code; they provide UIs for debugging capabilities, code completion, syntax highlighting, refactoring support, VCS integrations, and much, much more. That said, I do my python development in Sublime Text using the Jedi autocomplete library (https://github.com/davidhalter/jedi https://github.com/davidhalter/jedi).