Editing vertex without removing true curves using ArcPy

Question

ArcMap 10.7.1 — Oracle 18c SDE.ST_GEOMETRY

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I have a polyline FC that has true curves.

And I have an ArcPy script that updates the M-values of the vertices in the lines:

import arcpy
connection = "Database Connections\my_conn.sde"
feature_class = connection + "\my_owner.my_fc"
spatial_reference = arcpy.Describe(feature_class).spatialReference

with arcpy.da.Editor(connection) as edit_session:
    with arcpy.da.UpdateCursor(feature_class, "SHAPE@") as cursor:
        for row in cursor:
            geometry = row[0].densify("ANGLE", 10000, 0.174533)
            parts = arcpy.Array()
            for part in geometry:
                points = arcpy.Array()
                for point in part:
                    point.M = geometry.measureOnLine(point)
                    points.append(point)
                parts.append(points)
            row[0] = arcpy.Polyline(parts, spatial_reference)
            cursor.updateRow(row)

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The script reconstructs and replaces the geometry of the lines. So, unfortunately, it removes the true curves from the shapes.

Before running script:

After running script:

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Question:

With ArcPy, is there a way to edit vertices without removing true curves from the SHAPE?

For example, is there way to do something like this?

UpdateVertex (shape, partNum, vertexNum, [x, y, z, m]) 

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Related:

True Curves = True Evil

Idea: ArcPy - Edit vertex without removing true curves

Answer 1

I guess you can manipulate it using JSON.

For example, this field calculator expression, when I run it on a buffer of a point:

import json
def wJson(shp):
 pnts = json.loads(shp.JSON)
 #esriJSON = arcpy.AsShape(pnts, True)
 return str(pnts)
#----
wJson( !Shape!)

Returns:

{u'curveRings': [[[1727075.9359999998, 5946765.4923], {u'a': [[1727075.9359999998, 5946765.4923], [1717013.4664801424, 5946765.4923], 0, 1]}]], u'spatialReference': {u'wkid': 2193, u'latestWkid': 2193}}

Which is just a dictionary. You can use:

esriJSON = arcpy.AsShape(pnts, True)

after amending the dictionary.

Also see getPart() method returns incorrect geometry from buffer in ArcGIS