Every time I've rewritten something from Python into Java, Scala, or Rust it has gotten around ~30x faster. Plus, now I can multithread too for even more speedups.

Python is absurdly slow - every method call is a string dict lookup (slots are way underused), everything is all dicts all the time, the bytecode doesn't specialize at all to observed types, it is a uniquely horrible slow language.

I love it, but python is almost uniquely a slow language.

Algorithms matter, but if you have good algorithms, or you're already linear time and just have a ton of data, rewriting something from a single-threaded Python program to a multithreaded rust program I've seen 500x speedups, where the algorithms were not improved at all.

It's the difference between a program running overnight vs. in 30 seconds. And if there are problems, the iteration speed from that is huge.

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eru 2 hours ago | parent | next [-]

> [...], it is a uniquely horrible slow language.

To be fair, Python as implement today is horribly slow. You could leave the language the same but apply all the tricks and heroic efforts they used to make JavaScript fast. The language would be the same, but the implementations would be faster.

Of course, in practice the available implementations are very much part of the language and its ecosystems; especially for a language like Python which is so defined by its dominant implementation of CPython.

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jmalicki 2 hours ago | parent [-]

Fair! I guess I didn't mean language as such, but as used.

But a lot of the monkey-patching kind of things and dynamism of python also means a lot of those sorts of things have to be re-checked often for correctness, so it does take a ton of optimizations off the table. (Of course, those are rare corner cases, so compilers like pypy have been able to optimize for the "happy case" and have a slow fall-back path - but pypy had a ton of incompatibility issues and now seems to be dying).

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dtech 2 hours ago | parent [-]

Javascript has a lot of the same theoretical dynamism, yet V8 and WebkitCore were able to make it fast

	▲	eru 30 minutes ago \| parent [-]
		Yes, with heroic effort. It's really a triumph of compiler / vm engineers over language designers.

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byroot 2 hours ago | parent | prev [-]

> every method call is a string dict lookup

Doesn't the Python VM have inline caches? [0]

https://en.wikipedia.org/wiki/Inline_caching

	▲	jmalicki 2 hours ago \| parent [-]
		I think that's a new thing from like python 3.12+ or something after I stopped using Python as much. It didn't used to. EDIT: python 3.11+: https://peps.python.org/pep-0659/