Replace PreciseFlexJointCoords with PFAxis IntEnum + dict (#901)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: rickwierenga

docs/user_guide/01_material-handling/arms/c_scara/precise-flex-pf400/hello-world.ipynb

@@ -32,7 +32,7 @@
     "from pylabrobot.arms.precise_flex.pf_400 import PreciseFlex400Backend\n",
     "\n",
     "from pylabrobot.arms.precise_flex.coords import PreciseFlexCartesianCoords\n",
-    "from pylabrobot.arms.precise_flex.joints import PreciseFlexJointCoords\n",
+    "from pylabrobot.arms.precise_flex.joints import PFAxis\n",
     "from pylabrobot.resources import Coordinate, Rotation"
    ]
   },
@@ -144,14 +144,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "location = PreciseFlexJointCoords(\n",
-    "  base=99.981,\n",
-    "  shoulder=-36.206,\n",
-    "  elbow=83.063,\n",
-    "  wrist=-331.7,\n",
-    "  gripper=126.084,\n",
-    "  rail=0.0\n",
-    ")\n",
+    "location = {\n",
+    "  PFAxis.BASE: 99.981,\n",
+    "  PFAxis.SHOULDER: -36.206,\n",
+    "  PFAxis.ELBOW: 83.063,\n",
+    "  PFAxis.WRIST: -331.7,\n",
+    "  PFAxis.GRIPPER: 126.084,\n",
+    "  PFAxis.RAIL: 0.0,\n",
+    "}\n",
     "await arm.move_to(location)"
    ]
   },

pylabrobot/arms/backend.py

@@ -1,9 +1,8 @@
 from abc import ABCMeta, abstractmethod
 from dataclasses import dataclass
-from typing import Optional, Union
+from typing import Dict, Optional, Union
 
 from pylabrobot.arms.precise_flex.coords import PreciseFlexCartesianCoords
-from pylabrobot.arms.standard import JointCoords
 from pylabrobot.machines.backend import MachineBackend
 
 
@@ -78,20 +77,20 @@ async def move_to_safe(self) -> None:
   @abstractmethod
   async def approach(
     self,
-    position: Union[PreciseFlexCartesianCoords, JointCoords],
+    position: Union[PreciseFlexCartesianCoords, Dict[int, float]],
     access: Optional[AccessPattern] = None,
   ) -> None:
     """Move the arm to an approach position (offset from target).
 
     Args:
-      position: Target position (CartesianCoords or JointCoords)
+      position: Target position (CartesianCoords or joint position dict)
       access: Access pattern defining how to approach the target.  Defaults to VerticalAccess() if not specified.
     """
 
   @abstractmethod
   async def pick_up_resource(
     self,
-    position: Union[PreciseFlexCartesianCoords, JointCoords],
+    position: Union[PreciseFlexCartesianCoords, Dict[int, float]],
     plate_width: float,
     access: Optional[AccessPattern] = None,
   ) -> None:
@@ -105,7 +104,7 @@ async def pick_up_resource(
   @abstractmethod
   async def drop_resource(
     self,
-    position: Union[PreciseFlexCartesianCoords, JointCoords],
+    position: Union[PreciseFlexCartesianCoords, Dict[int, float]],
     access: Optional[AccessPattern] = None,
   ) -> None:
     """Place a plate at the specified position.
@@ -116,11 +115,11 @@ async def drop_resource(
     """
 
   @abstractmethod
-  async def move_to(self, position: Union[PreciseFlexCartesianCoords, JointCoords]) -> None:
+  async def move_to(self, position: Union[PreciseFlexCartesianCoords, Dict[int, float]]) -> None:
     """Move the arm to a specified position in 3D space or in joint space."""
 
   @abstractmethod
-  async def get_joint_position(self) -> JointCoords:
+  async def get_joint_position(self) -> Dict[int, float]:
     """Get the current position of the arm in joint space."""
 
   @abstractmethod

pylabrobot/arms/precise_flex/joints.py

@@ -1,24 +1,10 @@
-from dataclasses import dataclass
-from typing import Iterator
+from enum import IntEnum
 
 
-@dataclass
-class PreciseFlexJointCoords:
-  base: float
-  shoulder: float
-  elbow: float
-  wrist: float
-  gripper: float
-  rail: float = 0
-
-  def __iter__(self) -> Iterator[float]:
-    return iter(
-      [
-        self.rail,
-        self.base,
-        self.shoulder,
-        self.elbow,
-        self.wrist,
-        self.gripper,
-      ]
-    )
+class PFAxis(IntEnum):
+  BASE = 1
+  SHOULDER = 2
+  ELBOW = 3
+  WRIST = 4
+  GRIPPER = 5
+  RAIL = 6