With Python, my learning process has been very adhoc, because I never really set out to learn it; I mostly picked it up by fixing internal automation tools and tacking bits on to them. However, I've really fallen in love with it over time and see it playing a major part in my future, so I decided to formalize that learning.
A couple of companies offer Python certifications, however I decided to stick with the Python Institute's offerings. They offer two possible starting points on their certification path: the PCEP (Entry-Level Python Programmer) and the PCAP (Certified Associate in Python Programming). The PCEP is a optional stepping stone on their certification path as a percussor to the PCAP.
I started out with the PCEP. With hindsight this may have been a bad idea, as it's not a requirement for the Associate level exam and the difficulty of the exam content is the same - it just has less of it. It is much cheaper though, is available online at anytime without proctoring, and was good for building confidence in my skills.
I later decided to take the PCAP exam as well. It requires a bit more studying and is normally an in person exam taken in a Person Vue centre, though they have offered it online for a bit with COVID.
The Python Institute offer free courses which go over the exam in real detail and basically teach you from the ground up - you don't really need anything else. I worked through both parts of the relevant course and, to be honest, I'm very impressed at what they offer - they really seem to care about candidates and want to help them succeed instead of just get money out of them. As well, if you pass the practice exams on schedule, they offer a 50% off voucher for the PCAP exam.
The courses are extremely high quality, but they are all text (with activities and pictures obviously), which works really well for me, especially as it let me skim read where I knew the area already. I did a separate course with Linux Academy as well for the PCEP exam, which was good but I really didn't need to do it and there was some stuff that didn't seem to align with the exam objectives.
I'd recommend doing the Python Institute's courses even if you really know Python, as the exam objectives are somewhat deceptively simple; it covers a number of obscure areas like bitwise operators that you might never have encountered before. The practice exams are really good as well for getting a feel for the exam.
I took both exams online. With them not being proctored, I skim read the course to get an idea of how much time I needed to do it, and blocked out the time for it, and started the exam the moment I was happy with my knowledge and understanding. This worked really well for me because I knew the language well enough/am a fast enough reader to plough though the courses in about 1.5 days, though of course your milage may vary.