Full disclosure, I hate Python. I use it everyday for work and I hate it. I grew up on low level languages and Python never feels like "real programming." That's obviously nonsense, it's just how I feel. But...
Without a specific goal in mind, Python is a safer bet. Regardless of your project, you'll get up and running faster in Python and can build a proof of concept. If it turns out that speed is an actual issue, you can rebuild it in a lower level language (might I also suggest Rust) and you'll be able to build it faster and better already having experience in the specific problem domain. And maybe you just need to build small parts in C/C++ and can call that highly optimized code via Python.
Truly, Python is often like a fairy-tale. It's very easy to learn and code with, but the community has a mantra that there should be one, and only one, correct "Pythonic" way to do something. Frankly, they can be quite hostile about it, which is another reason I'm not a fan. But, honestly, maybe they're right. The most efficient, best implementation isn't always, or often, the cleanest, so even though it's easy to write in, it's not always easy to get right.
Without a specific use case, if you do think of a project that would do well as a library that any or all other languages could use or call, reach for C/C++. Otherwise, start in Python. Anything else is likely "premature optimization."