I don't hear nearly as much about Julia as I used to. A few years ago the view was that it was about to replace Python as the language of choice for data science. Seems like that didn't happen?

I think the hype has slowed down, but all growth statistics haven't. Personally, I think Julia is the only language where I can implement something like Makie without running into a maintenance nightmare, and with Julia GPU programming is actually fun and high level and composes well, which I miss in most other languages. So, I dont really care about it replacing python or not. I do think for replacing python Julia will need to solve compilation latency, shipping AOT binaries and maybe interpret more of the glue code, which currently introduces quite a lot of compilation overhead without much gains in terms of performance.

I don't know about everyone else, but slow Julia compilation continues to cause me ongoing suffering to this day. I don't think they're ever going to "fix" this. On a standard GitHub Actions Windows worker, installing the public Julia packages I use, precompiling, and compiling the sysimage takes over an hour. That's not an exaggeration. I had to juice the worker up to a custom 4x sized worker to get the wall clock time to something reasonable.

It took me days to get that build to work; doing this compilation once in CI so you don't have to do it on every machine is trickier than it sounds in Julia. The "obvious" way (install packages in Docker, run container on target machine) does not work because Julia wants to see exactly the same machine that it was precompiled on. It ends up precompiling again every time you run the container on other machines. I nearly shed a tear the first time I got Julia not to precompile everything again on a new machine.

R and Python are done in five minutes on the standard worker and it was easy; it's just the amount of time it takes to download and extract the prebuilt binaries. Do that inside a Docker container and it's portable as expected. I maintain Linux and Windows environments for the three languages and Julia causes me the most headaches, by far. I absolutely do not care about the tiny improvement in performance from compiling for my particular microarch; I would opt into prebuilt x86_64 generic binaries if Julia had them. I'm very happy to take R's and Python's prebuilt binaries.

Versus Python, it seems to fork into the "thinkers" vs "doers" camp. Julia provides a level of abstraction that some people find comforting. I thought I could use it as a sort of open source Matlab for a lot of thinky, 1-based index code I had lying around. It didn't meet my needs. And "spend half an hour waiting for a Jupyter notebook to boot up" is real. Great for some but it's not compatible with the way I work.

Elsewhere someone used the term "janky" and perhaps it's the fact that there are so many incredibly smart people around it that makes it so janky. By way of example, somebody needed to check disk space and the architect told him to shell out to Python.

Remember when LLVM first came out and it got kudos for the quality of its error messages? Well if you miss the old-school 1980s GCC experience the nonsense that eventually comes out of the Julia compiler after an hour will relight that flame.

Want to use greek letters and other symbols that don't appear on your keyboard as variable names? You've found your people.

As someone who currently uses dabbles in both. That prediction seems a bit unrealistic. Julia is a fantastic language but it has some trade offs that need to be considered. Probably the most well known is `time to first x`. Julia like Python is used comfortably in notebooks but loading libraries can take a minute, compared to Python where it happens right away. It may lead you to not reach for it when you want to do quick testing of something especially plotting. You can mitigate this somewhat by loading all the libraries you'll ever need at startup (preferably long before you are ready to experiment) but that assumes you already know what libraries you'll need for what you're wanting to try.

Julia is great ... if you are willing to work with the Goldilocks zone it provides.

I think what happened is this: Julia got advertised as "Python syntax, C speed" but in practice it turns out to really be "Python syntax, 50% of C speed if you were willing to avoid some semi-well-documented gotchas, where avoiding said gotchas will take some non-trivial effort". Again, great if you are willing to work with it.

I am not saying that the Julia people are responsible for the "Python syntax, C speed" perception as much as that was what the prevalent perception became. And

I have talked to people in computational biology who tried Julia, and they said something or the other similar to "It just wasn't performant enough for me to give up Python," and if you really dig in, what really happened was when new people tried Julia with old mental models, they walked away thinking, "Heh, more MIT hypeware."

Ugh, this almost feels like flame-bait. This question invariably leads to a lot of bike-shedding around comments from people who feel strongly about some choices in the Julia language (1-based indexing and what not), and the fact that Julia is still not as polished as some other languages in certain aspects of developer experience.

"Data science" is an extremely broad term, so YMMV. That said, since you asked, Julia has absolutely replaced Python for me. I don't have anything new to add on the benefits of Julia; it's all been said before elsewhere. It's just a question of exactly what kind of stuff you want to do. Most of my recent work is math/algorithms flavored, and Python would be annoyingly verbose/inexpressive while also being substantially slower. Julia also tends to have many more high-quality packages of this kind that I can quickly use / build on.

IMO it just had too many rough edges. Very slow compilation, correctness issues (https://yuri.is/not-julia/), kinda janky tooling (not nearly as bad as pip tbf). Even basic language mistakes like implicit variable declaration and 1-based indexing (in 2012??).

Yes 1-based indexing is a mistake. It leads to significantly less elegant code - especially for generic code - and is no harder to understand than 1-based indexing for people capable of programming. Fight me.