Raymond Hettinger, Keynote on Concurrency, PyBay 2017

Threads are not hard. In fact, threads are extremely easy to implement. However, real Threading code is just incredibly difficult to reason, just by looking at it. This makes it easy for you to introduce race conditions without even knowing that there is one! There is also the fact that locks don't lock anything! They are just a flag, that a any code may choose to ignore. They are a not an enforcing tool, just a cooperative one. (More here: this video ) P.S. I created a library, that makes it easier to write safer multiprocessing code link

Notebooks may be suitable for scratching things, but not much else. The problems noted by the OP are very serious, specially in the scientific world, where many do not have proper software engineering skills. The real issue is that newcomers do not know better, and so they don't realize the damage they're inflicting upon themselves and others before it's too late (irreproducible code, hidden states, dep. management, etc). Even the fast.ai library, which is a wonder, has broken notebooks. For those who try to follow the course at home, trying to run the notebooks is frustrating, as things are out of order and so errors pop up all the time. Jeremy is a wonderful teacher, but compare following a Fast.ai course video, which uses notebooks, to following a python video from, e.g., Raymond Hettinger [2], which uses sphinx and a shell. While the documentation style and ugly shell don't look nearly as cool, they are so much clearer and better structured. Notebooks become popular because they fill one gap that was left uncovered. As the scientific community moves away from Matlab into Python and R, reading code - pushed, amongst others, by the popularity of Github - becomes a day-to-day activity. Matlab scripts were easily explorable because users would load them, set breakpoints here and there, and look at results interactively - exactly what notebooks aim to provide. The difference is that what used to be breakpoints now become cells, comments now turn into Markdown and figures are i

To say concurrency is broken in Python because of the GIL seems to be reiterated adage without actual wisdom behind it.[1] Are you writing an IO-bound task? Then asyncio[2] (even if just viewed as an interface: e.g., you can make it even more performant by using uvloop[3]) is a great way to achieve performant concurrency. As Raymond Hettinger likes to point out, even if you throw away the GIL, you will have to implement locks on shared resources (unless you're writing embarrassingly parallel codes--in which case either you can invoke them separately or use the multiprocessing module to great effect, or see how I do it easily below), and by the time you get all the locks implemented in your GIL-less world (locks which are error-prone), you've given up the performance you thought you'd get due to throwing away the GIL. Are you writing a CPU-bound task? I've only encountered this in scientific computing, as I'm a scientist, and for this (as another commenter mentions) I either use numpy[4] (strictly within a numpy call, the GIL is not held) or numba[5] (by default the entirety of your numba-fied functions do not hold the GIL). Therefore, I can either use Python threads or asyncio or Numba's built-in parallelism[6,7] (summary: some numpy routines for working with arrays of values are auto-parallized if called within a numba-fied function, and you can explicitly parallelize your own loops via `for i in numba.prange(N):`; in any case, then decorate the function with `@numba.njit(pa