set keyframes via t.animate(value=12, run_time=.5, mode=LINEAR)

blender_valuetracker.py

import bpy

# Predefined interpolation constants for auto-complete
BEZIER = ("BEZIER", None) 
LINEAR = ("LINEAR", None)      
EASE_IN = ("SINE", "EASE_IN")    
BOUNCE = ("BOUNCE", "EASE_OUT")   

class ValueTracker:
    def __init__(self, default_value=0, fps=24, name="Tracker"):
        self.fps = fps
        self.current_frame = 0
        obj = bpy.data.objects.get(name)
        if obj is None:
            bpy.ops.mesh.primitive_cube_add()
            obj = bpy.context.active_object
            obj.name = name

        if not obj.animation_data:
            obj.animation_data_create()
        if not obj.animation_data.action:
            obj.animation_data.action = bpy.data.actions.new(name + "_action")
        # Clear any existing fcurves
        for f in obj.animation_data.action.fcurves:
            obj.animation_data.action.fcurves.remove(f)
            
        self.obj = obj
        # Set the default value and insert an initial keyframe
        self.obj.location.z = default_value
        self.obj.keyframe_insert(data_path="location", frame=0, index=2)
        self.fcurve = obj.animation_data.action.fcurves.find(data_path="location", index=2)
        if self.fcurve is None:
            self.fcurve = obj.animation_data.action.fcurves.new(data_path="location", index=2)
        self.last_key_index = 0

    def animate(self, value, run_time, mode):
        """
        Animate the object's z-location to 'value' over 'run_time' seconds,
        applying the specified interpolation mode.

        :param value: Target z-location value.
        :param run_time: Duration of the animation in seconds.
        :param mode: A tuple like one of the predefined constants (BEZIER, LINEAR, EASE_IN, BOUNCE).
        """
        frames = int(run_time * self.fps)
        self.current_frame += frames
        self.obj.location.z = value
        self.obj.keyframe_insert(data_path="location", frame=self.current_frame, index=2)
        new_key_index = len(self.fcurve.keyframe_points) - 1

        if mode:
            interp, easing = mode
            self.fcurve.keyframe_points[self.last_key_index].interpolation = interp
            if easing:
                self.fcurve.keyframe_points[self.last_key_index].easing = easing

        self.last_key_index = new_key_index

# Create a ValueTracker instance and animate it using the new constants
t = ValueTracker(default_value=0, fps=24, name="Tracker")
t.animate(value=12, run_time=.5, mode=LINEAR)
t.animate(value=0, run_time=.5, mode=LINEAR)
t.animate(value=15, run_time=.5, mode=BEZIER)
t.animate(value=0, run_time=1.5, mode=BOUNCE)