If you know any other language(programming language) beforehand then you can even do it in one month
But even if you are an absolute beginner then also 3 months will be sufficient for you to learn python
But to master it you have to practice much more
'Learn Python' is too vague to give you a meaningful answer.
Learning enough to write simple text-based programs: Yeah, 3 months sound about right.
Being good enough for a job? Probably at least a year of intense work, more likely several years.
Knowing everything there is, like *fully* learn? Decades to never.
We can say this much: You won't get there in a hurry, you need to put in time and effort.