mirrors/ty
1
0
Fork 0
mirror of https://github.com/astral-sh/ty.git synced 2025-07-07 19:45:00 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 2

Minor clarifications in Python version docs (#344)

Browse source 
## Summary

This is unfortunately longer than what we had, but I thought that this
section could use some clarification. In particular, newer syntactic
features can not appear in `sys.version_info` branches, they will always
lead to errors.
This commit is contained in:
David Peter 2025-05-13 09:33:35 +02:00 • committed by GitHub
parent 8c5053f51e
commit a188aeb7b5
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
1 changed files with 15 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

21
docs/README.md
View file

@ -111,17 +111,26 @@ The Python version affects allowed syntax, type definitions of the standard libr
definitions of first- and third-party modules that are conditional on the Python version.
For example, Python 3.10 introduced support for `match` statements and added the
`sys.stdlib_module_names` symbol to the standard library. However, if your project also supports
Python 3.9, you cannot use these new features unless they are used in a `sys.version_info`
conditional branch:
`sys.stdlib_module_names` symbol to the standard library. Syntactic features always
need to be available in the lowest supported Python version, but symbols may be used
in a `sys.version_info` conditional branch:
```python
import sys
# `invalid-syntax` error if `python-version` is set to 3.9 or lower:
match "echo hello".split():
case ["echo", message]:
print(message)
case _:
print("unknown command")
# `unresolved-attribute` error if `python-version` is set to 3.9 or lower:
print(sys.stdlib_module_names)
if sys.version_info >= (3, 10):
print(sys.stdlib_module_names) # ok
else:
print(sys.stdlib_module_names) # error if `python-version` is set to 3.9 or lower
# ok, because the usage is guarded by a version check:
print(sys.stdlib_module_names)
```
By default, the lower bound of the project's [`requires-python`](<(https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#python-requires)>) field (from the `pyproject.toml`) is