Mailman 3 October 2018 - Python-ideas

Revisiting Immutable Mappings
by Philip Martin 18 Oct '18

18 Oct '18

Hi, I first want to thank everyone in the community for the contributions over the years. I know the idea of a frozendict has been proposed before and rejected. I have a use case for a frozendict implementation that to my knowledge was not discussed during previous debates. My reasoning for a frozendict class stems from patterns I typically see arise when performing ETL or data integrations and conversions. I generally have used MappingProxyType as a way to set default mapping to a function or to set an empty mapping to a function. I've created a gist with an example use case: https://gist.github.com/pmart123/493edf84d9aa61691ca7321325ebb6ab I've included an example of what code typically looks like when using MappingProxyType and what it could look like with a frozendict implementation. I believe this use case may also be under-reported in open source code as it often crops up when integrating third-party data sources, which at times can't be open sourced due to licensing issues. I would love to hear if anyone has used MappingProxyType in a similar manner, or if this use case could help warrant a frozendict in the standard library.

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Powerset
by Hasan Diwan 16 Oct '18

16 Oct '18

[if this isn't the correct spot, let me know and I'll gladly take it elsewhere] I have found myself needing powerset functionality several times recently to the point where I wondered if there's interest in making it part of the standard library. I have a working implementation and tests. Would take but 3 minutes to add it in and issue a pull request, but I'd like to know if there's interest from esteemed group members. Thanks for the quick turnaround. -- H -- OpenPGP: https://sks-keyservers.net/pks/lookup?op=get&search=0xFEBAD7FFD041BBA1 If you wish to request my time, please do so using bit.ly/hd1AppointmentRequest. Si vous voudrais faire connnaisance, allez a bit.ly/hd1AppointmentRequest. Sent from my mobile device Envoye de mon portable

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Support parsing stream with `re`
by Ram Rachum 12 Oct '18

12 Oct '18

Hi, I'd like to use the re module to parse a long text file, 1GB in size. I wish that the re module could parse a stream, so I wouldn't have to load the whole thing into memory. I'd like to iterate over matches from the stream without keeping the old matches and input in RAM. What do you think? Thanks, Ram.

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Introduce typing.SupportsFsPath
by robert.hoelzl＠posteo.de 12 Oct '18

12 Oct '18

Hello, Since __fspath__ was introduced in PEP 519 it is possible to create object classes that are representing file system paths. But there is no corresponding type object in the "typing" module. Thus I cannot specify functions, that accept any kind of object which supports the __fspath__ protocol. Please note that "Path" is not a replacement for "SupportsFsPath", since the concept of PEP 519 is, that I could implement new objects (without dependency to "Path") that are implementing the __fspath__ protocol. robert

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Paul Romer, 2018 Economics Nobel Laureate, uses Python and Jupyter
by Jonathan Fine 10 Oct '18

10 Oct '18

Terry Reedy wrote (to comp.lang.python) > https://paulromer.net/jupyter-mathematica-and-the-future-of-the-research-pa… > Jupyter, Mathematica, and the Future of the Research Paper > Paul Romer, new Nobel prize winner in economics, for research on how > ideas interact with economic growth, explained last April why he has > switched from Mathematica to Jupyter. Well done, Terry, for spotting this. I hope you don't mind, I've changed the subject to give Paul Romer star billing. I think he deserves it. Here's some URLs on Romer and Python. https://qz.com/1417145/economics-nobel-laureate-paul-romer-is-a-python-prog… https://developers.slashdot.org/story/18/10/09/0042240/economics-nobel-laur… https://www.reddit.com/r/Python/comments/9mhxq2/this_years_nobel_prize_in_e… https://news.ycombinator.com/item?id=18173812&ref=hvper.com&utm_source=hvpe… https://www.wsj.com/articles/nobel-in-economics-goes-to-american-pair-15389… And some related URLs https://www.nature.com/articles/d41586-018-01322-9 # Future of online publishing https://pypi.org/project/nobel/ # Python interface to Nobel Prize API! https://jfine2358.github.io/slides/2018-nature-jupyter-altair-vega-binder.h… And some Python code: >>> import nobel >>> api = nobel.Api() >>> api.prizes.filter(year=2018, category='economics')[0].laureates[1].surname u'Romer' -- Jonathan

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Re: [Python-ideas] add a time decorator to timeit.py
by Jonathan Fine 10 Oct '18

10 Oct '18

On 7 Oct 2018 20:39, "Michael Selik" <mike(a)selik.org> wrote: Isn't there some rule about noticing an undocumented feature, like, whoever pours the last cup of coffee needs to brew a fresh pot? :-) Most of the credit belongs, I think, to the original poster. His statement, that Python wasn't very Pythonic here, really drew attention to the empty coffee pot. -- Jonathan

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Re: [Python-ideas] Why is design-by-contracts not widely adopted?
by Hugh Fisher 09 Oct '18

09 Oct '18

> Date: Sun, 23 Sep 2018 07:09:37 +0200 > From: Marko Ristin-Kaufmann <marko.ristin(a)gmail.com> > To: Python-Ideas <python-ideas(a)python.org> > Subject: [Python-ideas] Why is design-by-contracts not widely adopted? [ munch ] > *. *After properly reading about design-by-contract and getting deeper into > the topic, there is no rational argument against it and the benefits are > obvious. And still, people just wave their hand and continue without > formalizing the contracts in the code and keep on writing them in the > descriptions. Firstly, I see a difference between rational arguments against Design By Contract (DbC) and against DbC in Python. Rejecting DbC for Python is not the same as rejecting DbC entirely. Programming languages are different, obviously. Python is not the same as C is not the same as Lisp... To me this also means that different languages are used for different problem domains, and in different styles of development. I wouldn't use DbC in programming C or assembler because it's not really helpful for the kind of low level close to the machine stuff I use C or assembler for. And I wouldn't use DbC for Python because I wouldn't find it helpful for the kind of dynamic, exploratory development I do in Python. I don't write strict contracts for Python code because in a dynamically typed, and duck typed, programming language they just don't make sense to me. Which is not to say I think Design by Contract is bad, just that it isn't good for Python. Secondly, these "obvious" benefits. If they're obvious, I want to know why aren't you using Eiffel? It's a programming language designed around DbC concepts. It's been around for three decades, at least as long as Python or longer. There's an existing base of compilers and support tools and libraries and textbooks and experienced programmers to work with. Could it be that Python has better libraries, is faster to develop for, attracts more programmers? If so, I suggest it's worth considering that this might be *because* Python doesn't have DbC. Or is this an updated version of the old saying "real programmers write FORTRAN in any language" ? If you are accustomed to Design by Contract, think of your time in the Python world as a trip to another country. Relax and try to program like the locals do. You might enjoy it. -- cheers, Hugh Fisher

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add a time decorator to timeit.py
by Amjad Ben Hedhili 08 Oct '18

08 Oct '18

I think that a time decorator will be a useful addition to the sandard library, as i find the current way of measuring execution time a bit tedious: timeit.timeit("fun_to_time(a, b)", setup="from __main__ import a, b", number=1) compared to: @timef def fun_to_time(a, b): ... or timef(print)("Hello world!"). I already made a basic implementation of it, and it's working well.

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Better error messages for missing optional stdlib packages
by Marcus Harnisch 08 Oct '18

08 Oct '18

Hi all When trying to import lzma on one of my machines, I was suprised to get a normal import error like for any other module. According to the docs lzma has been part of stdlib since 3.3. Further digging revealed that the error is due to the fact that xz wasn't compiled in when building Python. Since I suspect that there are other optional stdlib modules, this made me think whether the message in those cases should look a little more polished. Perhaps installing a stub module that prints some informative text before raising the relevant exception or similar. Also, maybe add a little note in the docs, stating that despite being part of stdlib this module might not be available on all systems. Thanks, Marcus

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Debugging: some problems and possible solutions
by Jonathan Fine 08 Oct '18

08 Oct '18

This thread is about debugging. I suggest we start by collecting problems and possible solutions. And that after about a week of that, we start discussing what we've gathered. We already have a problem and possible solution, provided by Eric Smith and Larry Hastings. <begin> TITLE: f-string "debug" conversion URL: https://mail.python.org/pipermail/python-ideas/2018-October/053956.html PROBLEM Writing print('value = ', value) is tedious, particularly for more complicated expressions, such as print('big_array[5:20] =', big_array[5:20]) POSSIBLE SOLUTION For f-strings, we add a !d conversion operator, which produces the text of an expression followed by its value. Thus, the two previous examples can be written more concisely as print(f'{value !d}') print(f'{big_array[5:20] !d}') </end> I suggest for the moment that we just gather problem-solution pairs, much as above. I think they'll be between 5 and 15 such pairs. I'll post one to the current discussion thread in an hour or so. And that after about a week, we move to discussing what we have. Finally, many thanks to Eric and Larry for their useful contribution to the important problem of debugging. -- Jonathan

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