I'm making a 2D platformer using my own engine in Python/Pygame and have made a good start. I've also made a level designer that exports the level tile map and the game imports it, but I need to associate different things, like switches that open specific doors (or to be more precise, pressure plates that hold a specific door open) but my tile map array currently only holds the tile image index number. What's the best way to include associated tiles (like which switch opens which door etc)?
Do I make an extra file with that data? Or do I have 2 values for each tile? I've tried Googling, but it's not really covered anywhere. I'm sure there's someone with this kind of experience out there... I don't really want to hard-code it in as I want the game to be as versatile as possible.
I would change your file format from storing one tile index per 2D cell to storing some more complex data object.  My first thought would be a dictionary per cell for maximum flexibility moving forward, but serializing that and storing it will be quite large.  There's a trade-off here between flexibility and storage size.
Another option would be using NamedTuples to store a fixed number of parameters per cell, while preserving a concise serialization.  NamedTuples are nice because they let you very concisely represent a data object in a way that both serializes well and can be queried into using named fields.
The questions you need to ask yourself are "what metadata do I need to know about each cell on the map" and "how much do I care about concise file size to represent them".
Best way to save a 2D Pygame platformer level tile map with extra data