mirror of
https://github.com/astral-sh/ty.git
synced 2025-07-08 03:54:59 +00:00
3634c41020
Splits each top-level heading of the existing documentation into a dedicated page as a starting point. --------- Co-authored-by: David Peter <mail@david-peter.de>
42 lines
1.8 KiB
Markdown
42 lines
1.8 KiB
Markdown
# Python version
|
|
|
|
The Python version affects allowed syntax, type definitions of the standard library, and type
|
|
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. 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):
|
|
# 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
|
|
used as the target Python version, ensuring that features and symbols only available in newer Python
|
|
versions are not used.
|
|
|
|
If the `requires-python` field is not available but a virtual environment *has* been
|
|
configured or detected, ty will try to infer the Python version being used from the virtual
|
|
environment's metadata.
|
|
|
|
If no virtual environment is present or inferring the Python version from the metadata fails,
|
|
ty will fall back to the latest stable Python version supported by ty (currently 3.13).
|
|
|
|
The Python version may also be explicitly specified using the
|
|
[`python-version`](./reference/configuration.md#python-version) setting or the
|
|
[`--python-version`](./reference/cli.md#ty-check--python-version) flag.
|