Well I "learned programming" in 1992 in the age of 12 with nothing else than a Microsoft Visual Basic book that came with my uncle's PC. So I think you are more than capable to learn any programming language in grad school.
About python: It's feasible to learn it in a month with some effort, every time on the toilet. That's how did it with this course https://www.oreilly.com/library/view/python-fundamentals/978...
For both of these examples I'd say the definition of "learn a language" and "learn programming" is important. For me it means learning to the point where you have a good overview about ideomatics and ecosystem and enough understanding to get done what you professionally oneedr as a hobbyist needs with the help of available documentation.
For example I work with C++ for at least a decade, but I always feel there is something new to learn or make better. Also there are endless framework specializations like Qt or similar that you could invest time on.
To sum up. Define your goal and then start learning. But I recommend not setting a goal like "know everything about the standard lib, humpy and pandas" - because everything is not required. Just enough to dig deeper while doing projects, the rest will come by itself (but never everything).
About your question weather it's worth, I would say yes. You will even become a better R programmer by looking beyond the edge of the plate, even if you will never use it. But I bet you will like it very much and start scalping Twitter for statistical research on a weekend 3 weeks from now with python.