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0 pointsmehrdadn6y ago0 comments

Python 3.7 to 3.8 broke some stuff. I was pretty annoyed to discover (the hard way) that e.g. this wouldn't run anymore:

  python3 -c "import ast; print(ast.arguments([]).args)"

It seemed completely unnecessary too. They could've just kept the structure the same across minor versions...

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5 comments · 2 top-level

takeda6y ago· 2 in thread

I think that probably lesson learned from python 2 -> 3 migration. It's probably better to introduce many small breaks than a big one?

The python despite having 3 digit versions apparently is not following semantic versioning. The major version number generally had not much significance (the python 3 was exception, 1->2 and what they are assuring us 3->4 won't be a big change)

mehrdadnOP6y ago

"Better" depends on your agenda. If it's to shove the next major version down users' throats, maybe it's easier to swallow small bites (bytes?) than one giant cow. If it's to provide a predictable and pleasant user experience, I'm less confident this is the right approach.

takeda6y ago

So I did look it up, they do provide a warning though (in the first paragraph):

"The ast module helps Python applications to process trees of the Python abstract syntax grammar. The abstract syntax itself might change with each Python release; this module helps to find out programmatically what the current grammar looks like."

This module is a bit special, because as they say, it supposed to reflect current python grammar. If they change grammar and didn't make it reflect it it would lead to different kinds of issues.

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brianwawok6y ago· 1 in thread

That is what is great about having a good test setup. You would know pretty quick if stuff broke. Which has been basically nothing for me (3.6 -> 3.7 -> 3.8)

mehrdadnOP6y ago

To be clear, the pain here was hunting down the root cause and fixing it when it shouldn't have broken in the first place, not the speed of discovering the problem after the code had already broken.

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