Is there a shared binary format between iOS and Python? I found binary property lists. 
I have a list of UIBeziarPaths in an array that I want to be able to send to Python. I am just looking for something that will very efficiently be able to do that. I looked into the text based formats like JSON except they seem less efficient than a binary format for this purpose.
There are no formats specifically designed for iOS/Python. There are numerous data interchange formats you could use, including protocol buffers, BSON, ASN.1 (if you're that way inclined) and even a range of binary XML serialisation formats.
OTOH, I would strongly favour JSON (a textual format) unless bandwidth is exceptionally tight.
EDIT: I was awfully remiss not to mention another strong contender for binary transmission: BERT. I would favour BERT over any other binary format, but note my comments to the original question regarding encoding size.
Shared binary format between iOS and Python