- you use softwares that are scriptable in Python (SIG, Blender, etc)
- you write a lot of glue code. That pretty much Python raison de vivre.
- you do a lot of data analysis manually. Pandas is the new excel, and jupyter the new matlab.
- you do a lot of sysadmin. Scripting is just easier in a dynamic language.
- you do a lot of CRUD websites. You just can't beat the frameworks from this language for this kind of things. They do most of the work for you, and do security better than you do.
- you want to integrate new members in your team faster. Python is easier to learn than lisp.
- you are coding a GUI. With kivy you can target desktop and mobile with one code base, and some skins are pretty (https://imgur.com/a/IjM0XGW). With QT you can do powerful things on the desktop. With wx you can do simple GUI simply.
- you have a lot of different kinds of task at hand, and don't want to have too many different languages in your stack. Python is never the best language at anything, but it's a damn good language for most things, so it makes it a versatile toolbox.