I want to buy an Arduino kit but not an official Arduino, from different company
My question is: Will it work with the Arduino IDE? Even if it not official?
Can I use Python with it?
Arduino is an open-source hardware and software project, Arduino IDE supports many Arduino-compatible boards, including official and non-official boards, here is a non-exhaustive list of compatible boards.
You can even make your own Arduino-compatible board and provide hardware platform/plugins for Arduino IDE.