Python Steering Council Unanimously Accepts "pep 810, Explicit Lazy Imports"

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Dear PEP 810 authors. The Steering Council is happy to unanimously [4 votes, as Pablo cannot vote] accept “PEP 810, Explicit lazy imports”. Congratulations! We appreciate the way you were able to build on and improve the previously discussed (and rejected) attempt at lazy imports as proposed in PEP 690.

We have recommendations about some of the PEP’s details, a few suggestions for filling a couple of small gaps, and we have made decisions on the alternatives that you’ve left to the SC, all of which I’ll outline below. If you have any questions, please do reach out to the SC for clarification, either here, on the SC tracker, or in office hours.

Use lazy as the keyword. We debated many of the given alternatives (and some we came up with ourselves), and ultimately agreed with the PEP’s choice of the lazy keyword. The closest challenger was defer, but once we tried to use that in all the places where the term is visible, we ultimately didn’t think it was as good an overall fit. The same was true with all the other alternative keywords we could come up with, so… lazy it is!

What about from foo lazy import bar? Nope! We like that in both module imports and from-imports that the lazy keyword is the first thing on the line. It helps to visually recognize lazy imports of both varieties.

Leveraging a subclass of dict. We don’t see a need for this complicated alternative; please add this to the rejected ideas.

Allowing ’*’ in __lazy_modules__. We agree with the rationale for rejecting this idea; it can always be added later if needed.

One thing that the PEP does not mention is .pth files, which the site.py module processes, and which has some special handling for lines that begin with the string 'import' followed by a space or tab. It doesn’t make much sense for .pth files to support lazy imports, so we suggest that the PEP explicitly says that this special handling in .pth files will not be adapted to handle lazy imports.

There currently is no way to get the active filter mode, so please add a sys.get_lazy_imports() function. Also, do you think appending _mode to their names makes the purpose of these functions clearer? We leave that up to the PEP authors.

The PEP should be explicit about the precedence order between the different ways to set the mode, i.e. $PYTHON_LAZY_IMPORTS=<mode>, -X lazy_imports=<mode>, and sys.set_lazy_imports(). In all expectation, it will follow the same precedence order as other similar settings, but the PEP should be explicit.

We agree that the PEP should take no position on any style recommendations for sorting lazy imports. While we generally like the idea of grouping lazy imports together, let’s leave that up to the linters and auto-formatters to decide the details.

That should just about cover it. Again, thank you for your work on this, as it’s been a feature so many in the Python community have wanted for so long. Given the earlier attempts and existing workarounds, we think this strikes exactly the right balance.

-Barry, on behalf of the Python Steering Council

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I suspect this change in Python will dramatically improve the performance of such large programs as well.

I’m unfamiliar with the PEP process. How long until this makes it into a Python version?

0.https://www.hudsonrivertrading.com/hrtbeat/inside-hrts-pytho...

    lazy import *

https://discuss.python.org/t/pep-810-explicit-lazy-imports/1...

If Meta also starts firing Python developers, development might return to normal.

1. Standard library imports.

2. Related third party imports.

3. Local application/library specific imports.

https://peps.python.org/pep-0008/#imports

Based on the examples in PEP 810, I suppose each group of regular imports can be followed by a group of lazy imports?

  import os
  import sys
  
  lazy import json
  
  import fastapi
  
  lazy import numpy
  
  import myapi
  import mymodels
  
  lazy import myutils
  
  ...