Python 3.8 wishlist

3.7 is in beta now, so I'm closing the old 3.7 wishlist (#103) and starting a new one :-). This isn't complete or fully-fleshed out, but to get us started, here's some stuff off the top of my head:

• Better MultiError support: the main two pain points are catching them, and printing them (in particular we can override sys.excepthook, but that doesn't help with other code that wants to print or capture tracebacks like IPython, pytest, raven, ...)

• Whatever we decide we need to improve handling of cancel scope/nursery interaction with generators. PEP 568 is one approach (#265). This is complicated because cancel scopes and nurseries have somewhat different needs. Or maybe we just want to disallow yielding from inside them... but that would also need some kind of help from the interpreter. Details: https://github.com/python-trio/trio/issues/264#issuecomment-418989328

• Motion on bpo-32561 would be neat (better performance for async file operations)

• Making KeyboardInterrupt protection more reliable:

  • bpo-29988
  • some way to make @enable_ki_protection atomic; for example, bpo-12857

• Try proposing a hook that runs on bare calls to async functions (so e.g. await f() doesn't call the hook, but f() does). Trio would make this an error (#79), asyncio would make it call ensure_future, twisted would call asDeferred, etc.

  • There was a longish discussion of this starting here

• Adding a signal.raise_ wrapper (bpo-35568, see also #816)

This is a broad Python 3.8 wishlist covering several independent proposals, with related discussions in issues #265, #264, #79, #816, the linked PEP, and the referenced bpo items. Start by choosing one item and reading its linked discussion; the work is done only when that item has a separately agreed scope and acceptance criteria.