Bevel with specified radius in python script I think this is kinda simple. I currently make a Bezier curve and set a circle curve as the bevel object.
R = 0.1

bpy.ops.curve.primitive_bezier_curve_add(align='WORLD', location=(0, 0, 0))
curve = bpy.context.active_object 

bpy.ops.curve.primitive_bezier_circle_add(radius=R, align='WORLD', location=(0, 0, 0), scale=(1, 1, 1))
cross_section = bpy.context.active_object

curve.data.bevel_object = cross_section
curve.data.use_fill_caps = True 
curve.data.bevel_mode = 'OBJECT'


This is all fine and I can set the circle radius to control the bevel radius. But I would like to make different radii at each end but still specified by a simple parameter:
R_1 = 0.1
R_2 = 0.3

I know this can be done with a taper curve but it not clear how to set the radius with parameters. Is there some simple/obvious/clever way to do this
Assuming you have a bezier curve with only 2 control points and you always want a circle for your shape, you can do this. I think this works, its past my bedtime, but copy paste in the text editor and it should work. Feel free to expand on your wishes.
import bpy

bpy.ops.curve.primitive_bezier_curve_add()
curve = bpy.context.active_object 

curve.data.use_fill_caps = True 
curve.data.bevel_mode = 'ROUND'     # Gives it a circle shape without needing another object as a profile.
curve.data.bevel_depth = 1          # 1 Meter Radius (NOT DIAMETER)

# These will multipy the curve radius at each control point, 
# so best to keep that at 1m and control the taper with these.
start_radius = 0.1  # Radius Multiplier 1
end_radius   = 0.3  # Radius Multiplier 2

# Assuming the curve type is 'BEZIER'
curve_points = curve.data.splines[0].bezier_points

# Assuming your curve only has 2 points.
curve_points[0].radius = start_radius
curve_points[1].radius = end_radius