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What's Coming in Python 3.8

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Re: What's Coming in Python 3.8

#181

Post by bulatb »

stefco_ wrote: post #171
kbd wrote: post #118

Despite controversy, walrus operator is going to be like f-strings. Before: "Why do we need another way to..." After: "Hey this is great". People are wtf-ing a bit about the positional-only parameters, but I view that as just a consistency change. It's a way to write in pure Python something that was previously only possible to say using the C api.

f-strings are the first truly-pretty way to do string formatting in python, and the best thing is that they avoid all of the shortcomings of other interpolation syntaxes I've worked with. It's one of those magical features that just lets you do exactly what you want without putting any thought at all into it. Digression on the old way's shortcomings: Probably the most annoying thing about the old "format" syntax was…

> If `str.dedent` was a thing

Have you looked at textwrap.dedent?

Re: What's Coming in Python 3.8

#182

Post by BuckRogers »

The problem with modern Python is that it's trying to recreate C# or Java. Which leaves it with nothing, because it'll only end up an inferior version of the languages/platforms of which it's attempting to duplicate.

When I was into Python, I liked it because it was a tighter, more to the basics language. Not having 4 ways to format strings and so forth. I don't think Python can defeat Java by becoming Java. It'll lose there due to multiple disadvantages. The way Python "wins" (as much as it could at least), is focusing on "less is more". They abandoned that a while ago.

My vision of a language like Python would be only 1-way to do things, and in the event someone wants to add a 2nd way, a vote is taken. The syntax is changed, and the old bytecode interpreter handles old scripts, and scripts written with the latest interpreter's bytecode only allows the new syntax. For me that's the joy of Python.

I think a lot of people wanted Python's original vision, "one way to do things". If I want feature soup, I'll use what I program in daily. Which I do want feature soup by the way, I just have no need to replace it with another "feature soup" language like Python turned into because it's inferior on technical and for me, stylistic levels.

Re: What's Coming in Python 3.8

#183

Post by dragonwriter »

txcwpalpha wrote: post #97
nneonneo wrote: post #74

Earlier quoted context omitted.

Regular = can only be used in statements. Walrus := can only be used in expressions. There's no overlap there. However, := does simplify certain expressions (like those nested if-else statements and the common "while chunk := read()" loop), which I think does justify its existence.

This honestly makes it seem more confusing to me. The fact that there is now an operator that can only be used in certain statements just makes things more confusing. And if there really is no overlap, then why wasn't the "=" operator just extended to also work in expressions? "while chunk = read()" seems like it makes just as much sense without adding the confusion of another operator.

> The fact that there is now an operator that can only be used in certain statements just makes things more confusing

The new operator (like many Python operators) can only be used in expressions (statements can contain expressions, but expressions are not a subset of statements.)

> The fact that there is now an operator that can only be used in certain statements just makes things more confusing

Because the “=” operator is the thing that defines an assignment statement. Even if this could be resolved unambiguously for language parsers, so that “statement defining” and “within expression” uses didn't clash, it would be create potential readability difficulties for human reading. Keeping them separate makes the meaning of complicated assignment statements and assignment-including expressions more immediately visually clear.

Re: What's Coming in Python 3.8

#185

Post by duckerude »

pmontra wrote: post #164
sametmax wrote: post #19

Earlier quoted context omitted.

F-strings have appeared 2 versions ago. All in all, the feedback we have has been overwhelmingly positive, including on maintenance and readability.

F-string are great and should have been in the language since the beginning. Many other languages had with their own version of them since version 0. What I don't understand is why Python needs a special string type when other languages can interpolate normal strings (Ruby, Elixir, JavaScript.)

f-strings need a prefix so old strings can keep working the same way.

If `print("{x}")` printed "{x}" in Python 3.5, it shouldn't print something else in a newer version. But `print(f"{x}")` was a syntax error before f-strings, so no code is broken by giving it a meaning.

JavaScript can't interpolate ordinary strings either, for the same reason. You need to use backticks (``).

Re: What's Coming in Python 3.8

#186

Post by [deleted] »

stefco_ wrote: post #171
kbd wrote: post #118

Despite controversy, walrus operator is going to be like f-strings. Before: "Why do we need another way to..." After: "Hey this is great". People are wtf-ing a bit about the positional-only parameters, but I view that as just a consistency change. It's a way to write in pure Python something that was previously only possible to say using the C api.

f-strings are the first truly-pretty way to do string formatting in python, and the best thing is that they avoid all of the shortcomings of other interpolation syntaxes I've worked with. It's one of those magical features that just lets you do exactly what you want without putting any thought at all into it. Digression on the old way's shortcomings: Probably the most annoying thing about the old "format" syntax was…

[deleted]

Re: What's Coming in Python 3.8

#187

Post by txcwpalpha »

thaumasiotes wrote: post #117
txcwpalpha wrote: post #105

Earlier quoted context omitted.

>Read it "if y" - that's what's being tested. Once way to test if this works is to take the code, read it aloud, and then use the read-aloud version to rewrite the code. If you don't have a high degree of certainty that you end up with the same code, something has failed along the way. In this case, if I take "if x:= y()" and read it aloud as "if y", I think the vast majority of people would translate that to code as…

You will end up with the same code under two conditions: 1. You read more than one line of code. 2. Executing the code in the conditional more than once doesn't matter. If you meet those two assumptions, then the reading I suggested will transform this if x := y(): act_on(x) into this if y(): act_on(y()) which is, in fact, the same thing.

That second point is quite an assumption to make. If it's okay to end up with the second one of your examples (without the ":=" operator), why did we need to add the walrus opeprator at all?

And if you're referring to this statement from your original comment:

> If variable_name, the substring from 3 to 5, is "fg", crash.

I don't find this to be a clear statement at all. If I read this aloud to any of my programming students, I doubt any of them would be able to decipher it into any code, let alone the code string which you've suggested.

Re: What's Coming in Python 3.8

#188

Post by locoman88 »

londons_explore wrote: post #70

I long for a language which has a basic featureset, and then "freezes", and no longer adds any more language features. You may continue working on the standard library, optimizing, etc. Just no new language features. In my opinion, someone should be able to learn all of a language in a few days, including every corner case and oddity, and then understand any code. If new language features get added over time, eventua…

Fully agree. If we continue with this madness in five years Python will become indistinguishable from the Python I learnt 10 years ago.

Seems the Golang people have much cooler heads. Time to push for Golang at my workplace

Re: What's Coming in Python 3.8

#189

Post by lxmcneill »

ohazi wrote: post #184

Also type hints for dictionaries with fixed keys: https://www.python.org/dev/peps/pep-0589/ I know it's almost always better to use objects for this, but tons of code still uses dictionaries as pseudo-objects. This should make bug hunting a lot easier.

Huh, was totally unaware of this. For me this has good implications for ingesting CSVs/.xlsx to dicts. Clean-ups / type hinting is required at times for dirtier documents.

Re: What's Coming in Python 3.8

#190

Post by dragonwriter »

chrisseaton wrote: post #51
gclaugus wrote: post #5

Walrus operator looks like a great addition, not too much syntax sugar for a common pattern. Why were folks arguing about it?

I don't know how you read it - 'if x is assigned the value y'? Most other things in Python can just be read out loud.

> I don't know how you read it

“... x := foo ...” is read “... x, which is foo, ...”

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