Loop through polyline vertices and update coordinate

Question

I have a Python 2.7 script that loops through GIS polylines and updates a coordinate.

The coordinate is called an "M" coordinate (aka a "Measure-value"). M coordinates are similar to X and Y coordinates, but are used for specialized linear referencing purposes.

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

with arcpy.da.Editor(connection) as editSession:
    with arcpy.da.UpdateCursor(fc, ["ASSET_ID", "SHAPE@"]) as cursor:
        for row in cursor:
            feature = row[1].densify ("ANGLE", 10000, 0.174533)
            partNum = 0
            partArray = arcpy.Array()
            for part in feature:
                pointArray = arcpy.Array()
                n = len(part)
                for i in range(n):
                    point = part.getObject(i)
                    point.M = feature.measureOnLine(point)
                    pointArray.append(point)
                partArray.append(pointArray)
                partNum += 1
            row[1] = arcpy.Polyline(partArray, spatialRef)
            cursor.updateRow(row)

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How can the script be improved?

Answer 1

Unfortunately, I have neither Python 2.7 nor some test data.

However, I would like to point out a few things:

• row[1].densify("ANGLE", 10000, 0.174533) returns a geometry (object), you may want to rename the variable to geometry
• partNum is not really used, you may want to get rid of it altogether
• There is no need to use range(n) since part is an array (arcpy.Array) and iterable
• Personally, I would call partArray just parts and pointArray just points (and use snake_case for variable names following the PEP8 style guide)

Below an example of the script with the suggested improvements. Note: Script is not tested but should work.

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, ["ASSET_ID", "SHAPE@"]) as cursor:
    
        for row in cursor:

            geometry = row[1].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[1] = arcpy.Polyline(parts, spatial_reference)

            cursor.updateRow(row)