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What’s New in Python 3.8

docs.python.org

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Re: What’s New in Python 3.8

#81

Post by jonnycomputer »

robocat wrote: post #30

def f(a, b, /, c, d, *, e, f): Wow: IMHO that is a very ugly syntax to define a fn with 6 parameters, although it looks to be a path dependency on previous decisions (*, and CPython ,/) and clearly there was much discussion of the need for the functionality and the compromises: https://www.python.org/dev/peps/pep-0570/ It amazes me to see how certain features make it into languages via community/committee (octal numb…

What bothers me is that the / is separated by commas, which makes it seem like the signature is one more than it actually is (even if that is not the case technically). I haven't looked too carefully here though.

Re: What’s New in Python 3.8

#82

Post by bratao »

The_rationalist wrote: post #42
bratao wrote: post #6

I do not know exactly what caused this, but my internal project test-suite got a much appreciated 5% speedup! Thank you Python team!

I you care about performance, maybe you should try pypy (the alternative python compiler)

I try PyPy every 3 months. It has improved greatly and for some periods I migrated to it. But for this particular project, most of time is spent inside lxml, pandas, scikit-learn and other extensions. CPython is actually faster than PyPy for this project. Maybe GraalVM / GraalPython can improve on this use-case.

Re: What’s New in Python 3.8

#83

Post by CivBase »

paulddraper wrote: post #73
CivBase wrote: post #22

As a developer who has primarily developed applications in Python for his entire professional career, I can't say I'm especially excited about any of the "headlining" features of 3.8. The "walrus operator" will occasionally be useful, but I doubt I will find many effective uses for it. Same with the forced positional/keyword arguments and the "self-documenting" f-string expressions. Even when they have a use, it's us…

> As a developer who has primarily developed applications in Python for his entire professional career, I can't say I'm especially excited about any of the "headlining" features of 3.8. Python is a fairly old, mature language. What features would you have been especially excited about?

The f-strings from 3.6 are a (relatively) recent feature that I have absolutely loved. I'd go so far as to say they are my favorite feature introduced by Python 3.

I'm also looking forward to PEP-554 [0], which allows for "subinterpreters" for running concurrent code without removing the GIL or incurring the overhead of subprocesses.

[0] https://www.python.org/dev/peps/pep-0554/

Re: What’s New in Python 3.8

#84

Post by mintplant »

fooblitzky wrote: post #49
Rebelgecko wrote: post #40

Earlier quoted context omitted.

>They didn't select my preferred syntax I don't write much python so there's probably something obvious I'm missing, but I don't see why they didn't use "=". Is there some significant difference between assignment expressions and assignment statements that makes it worth having distinct syntax?

It seems if you use '=' it leads to dangerous programming bugs[1], whereas ':=' somehow prevents those bugs? [1] https://effbot.org/pyfaq/why-can-t-i-use-an-assignment-in-an...

It's much easier to leave off one = when you meant == than it is to accidentally type :=

Re: What’s New in Python 3.8

#85

Post by grincho »

robocat wrote: post #56
BurningFrog wrote: post #32

Earlier quoted context omitted.

> which itself is a result of limiting ourselves to the ASCII symbols that can be typed I think we're ready for programming languages using some visually good Unicode characters, instead of overloading `[]{}!@#$%^&*()-_/` for everything!

There are programming fonts that use ligatures to convert >= to ≥, or -> to →, so the source code remains in ASCII but symbol sequences show as unique Unicode characters. A next step could be for common dev environments to actually convert symbol/key sequences to operators (how do APL programmers do it?) Avoiding ambiguity and semantic overloading of ASCII symbols would surely help beginners (if also given a UI that…

The Mac has provided easy access to symbols since 1984, with nice mnemonics like these:

    option-=  ≠
    option-  ≥
    option-/  ÷
    option-o  ø
    option-w  ∑
I don't know why other OSes haven't adopted something similar. The first couple of these were even idiomatic in HyperCard's scripting language.

Re: What’s New in Python 3.8

#86

Post by drdaeman »

geofft wrote: post #69
CivBase wrote: post #22

As a developer who has primarily developed applications in Python for his entire professional career, I can't say I'm especially excited about any of the "headlining" features of 3.8. The "walrus operator" will occasionally be useful, but I doubt I will find many effective uses for it. Same with the forced positional/keyword arguments and the "self-documenting" f-string expressions. Even when they have a use, it's us…

> The "walrus operator" will occasionally be useful, but I doubt I will find many effective uses for it. The primary one I want is if m := re.match(...): print(m.group(1)) and while s := network_service.read(): process(s) both of which are both clearer and less error-prone than their non-walrus variants. The other one that I would have found useful an hour ago is in interactive exploration with comprehensions. I freq…

Coming from Perl, I used to want this badly, but then I thought that there's absolutely nothing wrong with

    m = re.match(...)
    if m is not None:
        pass
Now, I wonder what you meant saying that single-line version is less error-prone, because I don't think so. I believe they're exactly the same in this regard, except for a bizarre case when someone would bastardize the code by putting some irrelevant lines between the assignment and the comparison, obfuscating the logic.

Also, as I tend to use `if m is not None:` rather than just `if m:` (because I typically don't want to run all that subtle `__nonzero__` magic), it would - subjectively - look less pretty in the one-line version: `if (m := re.match(...)) is not None:`.

Use in the generator expressions to create aliases/shortcuts and avoid repetition is great, though. I love this use case.

Re: What’s New in Python 3.8

#87

Post by [deleted] »

peterwwillis wrote: post #52
CivBase wrote: post #22

As a developer who has primarily developed applications in Python for his entire professional career, I can't say I'm especially excited about any of the "headlining" features of 3.8. The "walrus operator" will occasionally be useful, but I doubt I will find many effective uses for it. Same with the forced positional/keyword arguments and the "self-documenting" f-string expressions. Even when they have a use, it's us…

Perl devs have been using the walrus expression for decades, but we just called it "assigning a variable with local scope in an expression". $ perl $a = "foo"; if ( my $a = "bar" ) { print "$a\n" } print "$a\n" bar foo

[deleted]

Re: What’s New in Python 3.8

#88

Post by mintplant »

heyflyguy wrote: post #68

man do I wish they would make multiprocessing easier

Subinterpreters are coming in 3.9, which should fill most of the same roles as multiprocessing but without the complexities and edge cases of multiple real OS processes.

https://www.python.org/dev/peps/pep-0554/

Re: What’s New in Python 3.8

#89

Post by [deleted] »

kolinko wrote: post #39
CivBase wrote: post #22

As a developer who has primarily developed applications in Python for his entire professional career, I can't say I'm especially excited about any of the "headlining" features of 3.8. The "walrus operator" will occasionally be useful, but I doubt I will find many effective uses for it. Same with the forced positional/keyword arguments and the "self-documenting" f-string expressions. Even when they have a use, it's us…

I actually found an immense use for Walrus - used it to hack Python into doing pattern matching that is way more readable than without it: https://github.com/eveem-org/panoramix (source code for Eveem.org, which is arguably the best decompiler for Ethereum smart contracts out there. you can see a lot of pattern matching in pano/simplify.py , and I found no way to do it without extending the language/walrus while main…

[deleted]

Re: What’s New in Python 3.8

#90

Post by mark-r »

gizmo385 wrote: post #46
kolinko wrote: post #39

Earlier quoted context omitted.

I actually found an immense use for Walrus - used it to hack Python into doing pattern matching that is way more readable than without it: https://github.com/eveem-org/panoramix (source code for Eveem.org, which is arguably the best decompiler for Ethereum smart contracts out there. you can see a lot of pattern matching in pano/simplify.py , and I found no way to do it without extending the language/walrus while main…

After a quick read through, I personally find this syntax much harder to read using operator overloads than it would have been using a series of comparison functions. Tilde is a very obtuse operator and I don't know that this really buys you anything. Feels like a case of preferring cleverness over readability/usability/maintainability.

Exactly the road C++ tries to go down. How's that for a ringing endorsement?
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