How can I use Python to select one (spline control) point of a NURBS curve?

Question

How can I use Python to select one (spline control) point of a NURBS curve? I want to select and then move each point to a desired location. If this is not possible, I am happy to start with the locations and create a NURBS curve that ‘joins the dots’.

Answer 1

import bpy

for p in bpy.context.object.data.splines.active.points:
    p.co.z = p.co.z + 1
bpy.ops.object.mode_set(mode='EDIT')

This works.

UPDATE: (only change selected points)

bpy.ops.object.mode_set(mode='OBJECT')
counter = 0
for p in bpy.context.object.data.splines.active.points:
    print("counter = ",counter)
    if p.select == True:
        p.co.z = p.co.z - 1
        print("selected")
    counter = counter + 1
bpy.ops.object.mode_set(mode='EDIT')

Answer 2

IMO would join the dots.

I want to select and then move each point to a desired location.

If the idea is to take a set of points and "join the dots" it is quite possibly a lot simpler to to create the spline.

Here is an example using NURBS answser from Create curve from Numpy Array using Python

Result displayed in EDIT mode, after running script in OBJECT mode

Set the coordinates as desired, run the script in object mode, creates a curve object with control points at the input coordinates. Removes need to select points, mode toggle, and use operators.

Using numpy and in particular foreach_get(set) is going to be way quicker for a lot of points.

In this example have given each 4D NURB coordinate a weight w of 1.

import bpy
import numpy as np
def flatten(*args):
    c = np.empty(sum(arg.size for arg in args))
    l = len(args)
    for i, arg in enumerate(args):
        c[i::l] = arg
    return c
context = bpy.context
x, y, z = np.array(
    (
        (0, 0, 0),
        (1, 1, 1),
        (0, 1, 1),
        (0, 0, 1),
    )
).T
w = np.ones(len(x))
cu = bpy.data.curves.new(name="poly", type='CURVE')
cu.dimensions = '3D'
spline = cu.splines.new('NURBS') # poly type
spline is created with one point add more to match data
spline.points.add(x.size - 1)
spline.points.foreach_set("co", flatten(x, y, z, w))
spline.use_endpoint_v = True
spline.use_endpoint_u = True
ob = bpy.data.objects.new("NURBS", cu)

context.collection.objects.link(ob)
context.view_layer.objects.active = ob
ob.select_set(True)

And for example sake,

running a loop and changing the weight assigned to the 4th coordinate

for j in range(1, 100, 10):
    w = np.ones(len(x))
    w[3] = j

Note.

If the desired result is to have the curve pass through the control points, it may be an idea to choose a curve type other than NURBS.