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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

#311

Post by ciupicri »

ygrechuk wrote: post #128
3PS wrote: post #92

Earlier quoted context omitted.

The issue, in my opinion, is when you want something like this: while m := f(many, args): # do stuff with m Now, if you're writing this in Python 3.7, you often end up with some code duplication: m = f(many, args) while m: # do stuff with m m = f(many, args) # duplicate Or something like this: while True: m = f(many, args) if not m: break # do stuff with m Personally, I consider the last version to be the most elegan…

Why not something like this: def f_iter(many, args): while True: m = f(many, args) if m: yield m else: raise StopIteration ... for m in f_iter(many, args): # do stuff with m This way you’re isolating all the initialization logic, error handling, etc. And you can focus on your domain logic in your client code.

Instead of raising StopIteration you could also just return from the function. You could also make it a bit shorter if you swap the if branches.

  def f_iter(many, args):
      while True:
          m = f(many, args)
          if not m:
              return
          yield m

Re: What’s New in Python 3.8

#312

Post by DonaldPShimoda »

metalliqaz wrote: post #2

This is the release that contains the controversial assignment expressions, which sparked the debate that convinced GvR to quit as BDFL. They didn't select my preferred syntax, but I'm still looking forward to using assignment expressions for testing my re.match() objects. I haven't used 3.8.0 yet but I hope its a good one because 2020 is the year that 2.7 dies and there will be a lot of people switching.

> I'm still looking forward to using assignment expressions for testing my re.match() objects.

The fact that this is the go-to example that everybody is using in justifying the introduction of the assignment expression convinces me that the real problem lies with the re module's API.

(To be clear: I will also be using assignment expressions for this case, but I don't think assignment expressions are really in line with the overall design of Python.)

Re: What’s New in Python 3.8

#313

Post by zb »

ciupicri wrote: post #311
ygrechuk wrote: post #128

Earlier quoted context omitted.

Why not something like this: def f_iter(many, args): while True: m = f(many, args) if m: yield m else: raise StopIteration ... for m in f_iter(many, args): # do stuff with m This way you’re isolating all the initialization logic, error handling, etc. And you can focus on your domain logic in your client code.

Instead of raising StopIteration you could also just return from the function. You could also make it a bit shorter if you swap the if branches. def f_iter(many, args): while True: m = f(many, args) if not m: return yield m

Instead of raising StopIteration you have to return from the function, otherwise you'll just get a RuntimeError starting with Python 3.7.

Re: What’s New in Python 3.8

#314

Post by trymas »

tvelichkov wrote: post #309
trymas wrote: post #228

Earlier quoted context omitted.

IMHO walrus operator goes against the zen of python. https://www.python.org/dev/peps/pep-0572/#differences-betwee... https://www.python.org/dev/peps/pep-0572/#relative-precedenc... Even examples of the spec shows how unintuitive and "unpythonic" this is. Explicit is better than implicit. IMHO adding features to the language to save 1 line of code for 10% of cases when you need it (I agree that there's occasional case…

Well the zen of python also states: - Complex is better than complicated. Using the walrus operator makes the code more complex, but less complicated.

It also states one line before:

> Simple is better than complex.

I understand that nobody will force me to use this feature, but as I said before, even the spec and the write up tells how this feature is confusing and .. complex.

Re: What’s New in Python 3.8

#315

Post by ewidar »

jtdev wrote: post #111
Pxtl wrote: post #66

Ugh, I hate assignment expressions. I liked that they were missing from Python. I've been coding in algolesque languages for 20 years and hiding assignments inside of expressions instead of putting them on the left like a statement has always tripped me up.

But, but, but... now you don’t need to write that extra line of code! It’s going to make everything sooooo much better, code will practically write itself now. I’ll just leave this here: “There should be one—and preferably only one—obvious way to do it.”

Well there is now one obvious way to do most things that are targeted by this change, using the walrus operator.

Re: What’s New in Python 3.8

#316

Post by fjp »

DonaldPShimoda wrote: post #312
metalliqaz wrote: post #2

This is the release that contains the controversial assignment expressions, which sparked the debate that convinced GvR to quit as BDFL. They didn't select my preferred syntax, but I'm still looking forward to using assignment expressions for testing my re.match() objects. I haven't used 3.8.0 yet but I hope its a good one because 2020 is the year that 2.7 dies and there will be a lot of people switching.

> I'm still looking forward to using assignment expressions for testing my re.match() objects. The fact that this is the go-to example that everybody is using in justifying the introduction of the assignment expression convinces me that the real problem lies with the re module's API. (To be clear: I will also be using assignment expressions for this case, but I don't think assignment expressions are really in line wi…

re's API sucks but I'm looking forward to safe dictionary access with assignment as well. No more

if my_map.get(key) is not None:

    // do something with my_map[key]

Re: What’s New in Python 3.8

#317

Post by newen »

bouncing wrote: post #254
trymas wrote: post #228

Earlier quoted context omitted.

IMHO walrus operator goes against the zen of python. https://www.python.org/dev/peps/pep-0572/#differences-betwee... https://www.python.org/dev/peps/pep-0572/#relative-precedenc... Even examples of the spec shows how unintuitive and "unpythonic" this is. Explicit is better than implicit. IMHO adding features to the language to save 1 line of code for 10% of cases when you need it (I agree that there's occasional case…

I've been using Python since 1.5 and I feel like the language itself has been feature-complete for some time. In the 2.0 era, the big pain points were async and unicode; as demonstrated by, well, how painful Twisted's unicode was. ;) But now if our big paint point is assigning a variable to len(), then in two lines evaluating that variable and printing it out, Python is just trying to find stuff to add. I miss the si…

Yeah. I don't like this obsession that so many developers have with adding features without end. I think it's mostly so that they can have something to do; don't think about the bigger problems, just have something to do so that they can fill out their timesheets and submit it at the end of the week.

Re: What’s New in Python 3.8

#318

Post by bvrmn »

ygrechuk wrote: post #128
3PS wrote: post #92

Earlier quoted context omitted.

The issue, in my opinion, is when you want something like this: while m := f(many, args): # do stuff with m Now, if you're writing this in Python 3.7, you often end up with some code duplication: m = f(many, args) while m: # do stuff with m m = f(many, args) # duplicate Or something like this: while True: m = f(many, args) if not m: break # do stuff with m Personally, I consider the last version to be the most elegan…

Why not something like this: def f_iter(many, args): while True: m = f(many, args) if m: yield m else: raise StopIteration ... for m in f_iter(many, args): # do stuff with m This way you’re isolating all the initialization logic, error handling, etc. And you can focus on your domain logic in your client code.

Python has built-in facilities for that, there is no need to write wrapper by yourself.

   from functools import partial
   with open('mydata.db', 'rb') as f:
       for block in iter(partial(f.read, 64), b''):
           process_block(block)

Re: What’s New in Python 3.8

#319

Post by thanatropism »

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…

> Over complicating a language with rarely-used features can definitely create problems.

Agreed.

There's a number of (full) languages that compile to the Python AST [0] (I'm especially fond of http://hylang.org), but they're very different from Python. It would be interesting to see smaller variations of standard Python implemented in an interoperable way like these languages do.

[0] https://github.com/vindarel/languages-that-compile-to-python

Re: What’s New in Python 3.8

#320

Post by mark-r »

wolco wrote: post #106
mark-r wrote: post #90

Earlier quoted context omitted.

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

C++ is one of the most successful languages.

How much of that success can be attributed to the features that were added in the last 10 years?
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