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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

#101

Post by Tommah »

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…

There is a similar trick that you can use without the walrus operator. I wrote the code many years ago and I am reproducing this from memory, so the code below may be a little off. Define this class:

    class Any:
        def __eq__(self, other):
            self.value = other
            return True
Then you can use an instance of it as the hole in a pattern. My use case was performing peephole optimizations in a simple 6502 assembler. For example, if the LDA operation (load value from memory location into accumulator) occurs twice in a row, the first load is redundant. So I did this test:

    x, y = Any(), Any()
    if L[i:i+2] == [('LDA', x), ('LDA', y)]:
        L[i:i+2] = [('LDA', y.value)]
(Note that the last line changes the length of the list, so it may be slow on large lists.)

I was going to write a blog post about this back then, but I never did. If anyone is interested, I can write it now.

Re: What’s New in Python 3.8

#103

Post by adjkant »

svnpenn wrote: post #100

> In this example, the assignment expression helps avoid calling len() twice: if (n := len(a)) > 10: print(f"List is too long ({n} elements, expected Um, no it doesnt?: a1 = [10, 20, 30] n1 = len(a1) if n1 > 2: print(f'{n1} is greater than two')

I'm not a huge fan of the := operator for Python for clarity and single one clear way reasons, but the draw is the saved line of code here that is the "help"

Re: What’s New in Python 3.8

#104

Post by emmelaich »

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 someone who has used Python for over 10 years and C, Perl, etc for over 20, I've been craving the walrus operator forever.

I love the walrus operator with a love that is unholy.

Re: What’s New in Python 3.8

#105

Post by aeyes »

ram_rar wrote: post #91

Does the python community care about concurrency at all? I havent seen anything new in terms of concurrency in a while. I might be wrong about this, but walrus operator seems like a gateway to writing obfuscated perlesque code.

3.8 brings shared memory to multiprocessing: https://docs.python.org/3/library/multiprocessing.shared_mem...

Re: What’s New in Python 3.8

#106

Post by wolco »

mark-r wrote: post #90
gizmo385 wrote: post #46

Earlier quoted context omitted.

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?

C++ is one of the most successful languages.

Re: What’s New in Python 3.8

#110

Post by egdod »

seunosewa wrote: post #54
egdod wrote: post #37

Earlier quoted context omitted.

Mature languages don’t introduce random new ugly syntax. I miss Guido already.

Actually, Guido approved the walrus operator. (In response to the justified backlash, instead of canceling the feature, he resigned as BDFL, which is not what anyone wanted)

I stand corrected.
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