Mailman 3 May 2022 - Python-ideas

PEP 671 (late-bound arg defaults), next round of discussion!
by Chris Angelico July 23, 2023

July 23, 2023

I've just updated PEP 671 https://www.python.org/dev/peps/pep-0671/ with some additional information about the reference implementation, and some clarifications elsewhere. *PEP 671: Syntax for late-bound function argument defaults* Questions, for you all: 1) If this feature existed in Python 3.11 exactly as described, would you use it? 2) Independently: Is the syntactic distinction between "=" and "=>" a cognitive burden? (It's absolutely valid to say "yes" and "yes", and feel free to … [View More]

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zip(x, y, z, strict=True)
by Ram Rachum Dec. 1, 2022

Dec. 1, 2022

Here's something that would have saved me some debugging yesterday: >>> zipped = zip(x, y, z, strict=True) I suggest that `strict=True` would ensure that all the iterables have been exhausted, raising an exception otherwise. This is useful in cases where you're assuming that the iterables all have the same lengths. When your assumption is wrong, you currently just get a shorter result, and it could take you a while to figure out why it's happening. What do you think?

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Typescript-Like Notational Shortcuts
by kevinlu1248＠gmail.com July 1, 2022

July 1, 2022

On the theme of the addition of pip operators to indicate union, I was wondering what people think of using the following shortcuts for type hints. * type[] be a short-hand for List[type] * [type1, type2, type3] be a shorthand for Tuple[type1, type2, type3] * similar ideas for dictionaries and callables with (perhaps with javascript-like arrow notations?) I just think something like this would be easier to read. For example, a lot of functions that return tuples generally are immediately … [View More]

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disallow assignment to unknown ssl.SSLContext attributes
by Thomas Grainger June 10, 2022

June 10, 2022

I was debugging some code that was using TLSv1.2 when I expected it to only support TLSv1.3, I tracked it down to a call to: context.miunimum_version = ssl.TLSVersion.TLSv1_3 it should have been: context.minimum_version = ssl.TLSVersion.TLSv1_3 I'd like invalid attribute assignment to be prevented at runtime

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Expand the try-expect syntax to support conditional expect block
by Nadav Misgav June 3, 2022

June 3, 2022

Hello, I was thinking of a way to expand the current try-expect block to support condinitial expect block. I was imagining the new syntax as try: expression block expect Exception if condition expression block where the expect expression block would only run if the condition is met else it would raise the exception, for example the following code try: config = get_config() except Exception: if use_default: config = default else: raise would be converted … [View More]

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Opt-in “iter def” and/or “gen def” syntax for generator functions
by armload_lakes0c＠icloud.com June 1, 2022

June 1, 2022

After getting used to writing async functions, I’ve been wanting use a similar syntax to declare generator functions. Something along the lines of `iter def my_iterator() -> T` and/or `gen def my_generator() -> (T, U, V)` Obviously, for backwards compatibility, this would need to be optional or have an opt-in mechanism. Would a feature like this be at all within the realm of possibility? I’d be happy to write up a much longer discussion if so. (I found a short discussion of such a … [View More]

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Python array multiplication for negative values should throw an error
by fjwillemsen＠icloud.com June 1, 2022

June 1, 2022

Hopefully this is not a duplicate of an existing thread or in the wrong section, first time posting here. In Python, array multiplication is quite useful to repeat an existing array, e.g. [1,2,3] * 2 becomes [1,2,3,4,5,6]. Multiplication by 0 yields an empty array: [1,2,3] * 0 becomes []. However, operations such as [numpy array] * -1 are very common to get the inverse of an array of numbers. The confusion here stems from the lack of type checking: while the programmer should check whether … [View More]

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Awaiting until a condition is met
by Aaron Fink May 30, 2022

May 30, 2022

Hello. I've been thinking it would be nice to be able to use await to suspend execution until a condition is met (as represented by a function or lambda which returns a boolean. Currently, as far as I can tell, the way to accomplish this is with a while loop which frequently checks the condition, suspending execution in between checks. My use case is in robotics, so I'll use that. Here's a minimal version of my current approach. start_moving_to(dest) while distance_to(dest) > tolerance: … [View More]

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Enhance flexibility of dataclass repr
by Steve Jorgensen May 30, 2022

May 30, 2022

The desire for this came up for me in relation to a set of dataclasses used to define a tree structure where each item has a reference to its parent. Including the complete expansion of the parent (with its children and its parent with its children, etc.) is WAY too much information, but at the same time, I do want to at least identify the parent. Currently, the only way to get what I'm looking for is to write a custom `__repr__` from scratch. It would be great if there was at least 1 way to … [View More]

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Provide an asynchronus equivalent to itertools.chain, and possibly more of itertools
by rammers2＠hotmail.co.uk May 28, 2022

May 28, 2022

I recently started to dive into asynchronous programming in Python. My program iterates over text from posts on a website and analyses it. I wanted to add the ability to asynchronously apply the same analysis to posts from multiple websites. It seemed likely to me that this would be something people commonly want to do, but I was surprised to find no built-in solution. There are a few relevant stack overflow posts: https://stackoverflow.com/questions/55299564/join-multiple-async-generators… … [View More]

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