Reuse TypeVars

src/scanspec/core.py

@@ -21,6 +21,8 @@
 from pydantic_core.core_schema import tagged_union_schema
 
 __all__ = [
+    "Axis",
+    "OtherAxis",
     "if_instance_do",
     "AxesPoints",
     "Frames",
@@ -199,7 +201,7 @@ def if_instance_do(x: C, cls: type[C], func: Callable[[C], T]):
 
 
 #: A type variable for an `axis_` that can be specified for a scan
-Axis = TypeVar("Axis")
+Axis = TypeVar("Axis", covariant=True)
 
 #: Alternative axis variable to be used when two are required in the same type binding
 OtherAxis = TypeVar("OtherAxis")

src/scanspec/specs.py

@@ -8,16 +8,18 @@
 from __future__ import annotations
 
 from collections.abc import Callable, Mapping
-from typing import Any, Generic, TypeVar, overload
+from typing import Any, Generic, overload
 
 import numpy as np
 import numpy.typing as npt
 from pydantic import Field, TypeAdapter, validate_call
 from pydantic.dataclasses import dataclass
 
 from .core import (
+    Axis,
     Frames,
     Midpoints,
+    OtherAxis,
     Path,
     SnakedFrames,
     StrictConfig,
@@ -49,12 +51,6 @@
 #: Can be used as a special key to indicate how long each point should be
 DURATION = "DURATION"
 
-#: A type variable for an `axis_` that can be specified for a scan
-Axis = TypeVar("Axis", covariant=True)
-
-#: Alternative axis variable to be used when two are required in the same type binding
-OtherAxis = TypeVar("OtherAxis")
-
 
 @discriminated_union_of_subclasses
 class Spec(Generic[Axis]):