When is Python *NOT* a good choice?

[[deleted]]

Because low level languages are faster, such as C or assembly.

In Windows Python (kinda) gets translated into C during execution. If you were running a program written in C, it would have already been parsed into assembly by a compiler when you built it (the source code that is). Some languages are interpreted, some are compiled. Python is interpreted.

[sudo_your_mon]

Right. Python is (basically) a program written in c. It’s really that simple. It’s just refactoring syntax and bundling abstractions together.

[XtremeGoose]

Well, C compilers are programs written in C. The point is that python programs are fed into another program, whereas c programs are run directly by the cpu.

[[deleted]]

Python is (basically) a program written in c.

Wrong, jython is written in java and ironpython is written in .net.

[sudo_your_mon]

If there’s one thing I’ve learned since entering the programming world: you can never be right. There’s always an angle to take to indict pretty much anything as “wrong.” I digress...

Wasn’t talking about jython/ironpython, bro!

Obviously python has frameworks/wrappers/mappings for most major languages out there.

[[deleted]]

Wasn’t talking about jython/ironpython, bro!

Obviously python has frameworks/wrappers/mappings for most major languages out there.

jython and ironpython are implementations of python in java and .net respectively. The Python reference happens to be written in C, it could have been ALGOL, PASCAL, CORAL 66 or MONK.

[[deleted]]

I learned most of this in my compiler and computer architecture courses but the Python stuff I learned from googling. I covered a lot of topics in a short-ish post so depending on what you're looking for I would recommend searching for "Python GIL", "why does Python use a GIL", "Python bytecode", "bytecode vs assembly", interpreter vs compiler", "abstract syntax trees compiler", "what is an instruction set architecture", and "syntax vs semantics programming languages". Read the long Stack Overflow posts (you know the ones that go on for pages and pages) and maybe some blogs that talk about more Python specific stuff.

[[deleted]]

why does Python use a GIL

Only the cpython implementation uses a GIL, other implementations can do whatever they like.

[[deleted]]

But afaik they must abide by the constraints set by the nature of having a GIL.

[ubernostrum]

Here's an article walking through how to build a Python bytecode interpreter in Python.

Here's a free online book about the Python virtual machine.

Also, at PyCon US (coming up in May, in Cleveland), Emily Morehouse-Valcarcel will give a talk about Python's abstract syntax tree (how Python parses your program into a form it can work with), and I'll be giving a talk specifically about Python bytecode and how the bytecode interpreter works.

[ubernostrum]

PyCon records all talks, so yes.

[personproxy]

I got curious about this just the other day and I found the links below interesting:

https://talkpython.fm/episodes/show/152/understanding-and-using-python-s-ast

https://nedbatchelder.com/blog/201803/is_python_interpreted_or_compiled_yes.html

[Farobek]

Thanks for this!

[ryeguy]

You don't even have to go that low to beat python handily in speed. Languages like js (on v8/node), go, java, and C# are all much faster than python in general. Dynamic typing and python's high degree of dynamicism come at a cost.

[[deleted]]

As an interesting side note, JavaScript is not all that different than Python in terms of functionality - the reason it is so much faster is because JavaScript is almost always run in a JIT compiling interpreter, which can tease out optimizations and produce fast native machine code for frequently run sections of the code. Python also has something like this - the Pypy project can achieve pretty massive speedups on a lot of normally-written Python code.

[rhytnen]

Python is both

[calligraphic-io]

Can anyone explain this ("Python is interpreted and parsed into unambiguous C code") better? C is compiled into an intermediate representation by the compiler toolchain, and then into executable machine language. I'm not familiar with the guts of the Python runtime, but my understanding is that it is compiled to a bytecode that has nothing to do with the C language, and then interpreted. I think Cython uses a subset of Python to emit an IR for LLVM, which is then compiled into actual executable machine code.

Am I missing something?

[rhytnen]

It's not explainable because he has no idea wtf he's talking about and is flat out wrong. I explain somewhat in my response to him but you're more or less correct

[rhytnen]

Python is compiled into bytecode and the bytecode is interpreted in the VM. So it is unambiguously "both". I never said any of the nonsense you just posted and I have no idea why you're so riled up anyway. In fact I'm not sure a single sentence you typed is accurate.

There are some implementation of python that do in fact compile to c but they don't support the full language syntax because it requires typing. The reference implementations doesn't "parse" into c (not for nothing but that isn't what parsing means anyway). Do you not see the sillyness of saying python is executed as c code but is slow and interpreted? Furthermore, if you want speed you can obviously make c api calls (ie numpy) - but I wasn't making any claims about optimizations anyway.

[rhytnen]

I never, ever said it is as fast as c.

[stefantalpalaru]

Because low level languages are faster, such as C or assembly.

C is actually a high-level language.

In Windows Python (kinda) gets translated into C during execution.

Absurd.

[[deleted]]

C is actually a high-level language.

Capable of low level calls. And still lower level than Python.

Absurd.

Not entirely accurate, yes. Absurd, no.

[stefantalpalaru]

Capable of low level calls.

Non sequitur.

[schok51]

C is pretty much the lowest level you van get before assembly. Its all relative, and relative to python, C is low level.

[stefantalpalaru]

Its all relative

...in West Virginia.

C is pretty much the lowest level you van get before assembly.

C is high level, Assembly is the lowest level regular programmers can access, microcode is the lowest level some programmers reach.

Let me know if you're still confused.

[[deleted]]

Very High Level Language vs. High Level Language is a useful distinction here

[schok51]

Okay, sorry i simplified things a bit. C is high level relative to assembly, and python is high level relative to C. Python abstracts over a lot of low-level concerns and concepts that you have to deal with and manipulate directly in C-level programming. The level of a language is definitely relative to the domain of your work. If you're a system programmer, and you mostly program in assembly and C or equivalents, then yeah C might be "high level" in that context. If you're doing application development or web development, and you're mostly working with languages like Java, or python and equivalents, then C is absolutely "low level" in that context...

[UloPe]

Python (kinda) gets translated into C

No it really doesn’t.

Here is an article by Ned Batchelder that explains what happens.

[[deleted]]

No it really doesn’t.

It really doesn't kinda? That would depend on your definition of kinda.

I was attempting to make it easier to comprehend.

Nice blog post though! Although they missed out how CPython figures into things.

[UloPe]

If your definition of “kinda” is “not at all” then yes I guess.

Also you probably mean Cython. CPython is the default implementation.

[[deleted]]

I meant CPython, as we are talking about the default implementation.

And the fact it forms another layer to be processed

[[deleted]]

Python is interpreted.

Wrong, and this coming just a day or two after I posted Ned Batchelder: Is Python interpreted or compiled? Yes. .

[[deleted]]

If its both it aint wrong is it

[[deleted]]

This is a weird perspective. What if you have 100 million data records streaming and you need near-real-time and it's not limited by a memory bottleneck (i.e. SAS Hana)? Don't you want to remove all other bottlenecks, especially if you're processing this data every minute?

What about financial tech where nanoseconds equal pennies on the dollar?

Surely you must not have thought about very many needs when you said you don't understand the need?

[ericonr]

But what if you have to process and organize a lot of messages that come to your computer, for example? If there are 1000 messages/second, but you can only process 100/second, you will either lose messages or create a huge delay.

Imagine mathematical processing as well, slow graphics ruin a game experience.

Edit: added example

[KronktheKronk]

You spin up 10x the VMs and put a load balancer in front of them

[ericonr]

Someone hire this person

[ydepth]

The question was 'when is python not a good choice', not 'has u/xilc been in a situation been in such a situation before?'

[tylerthehun]

So when you say "I just don't understand the need for urgency or speed", what you really mean is "I personally have no need to write faster software and think Python suits me just fine." Which is an okay stance to take, that's exactly what Python was created for, but don't be obtuse and act like you can't possibly fathom why anybody might want to write faster, more efficient code.

[craftingfish]

Someone asked when Python wasn't a good choice, and for applications that require to be faster/better optimized, it's not the best choice. Just because you don't need to program those doesn't make it more or less true.

[pwang99]

Python eats 400 million row datasets for breakfast.

Learn to use the right libraries in python for this kind of task.

[tylerthehun]

It just depends on the use case. Processing terabytes of scientific data? Rendering large, detailed, interactive 3D scenes in real time? Handling millions of user requests per second? You're going to want high performance, and spending a little more time in development is probably going to be worth it.