ArcPy (Pro): Look-Ahead Cursor

arcpy_pro_look_ahead_cursor.py

#!python3
# Reference: 1) https://pro.arcgis.com/en/pro-app/arcpy/data-access/searchcursor-class.htm
#            2) https://pro.arcgis.com/en/pro-app/arcpy/data-access/updatecursor-class.htm
#            3) https://docs.python.org/3/library/itertools.html

import arcpy
from itertools import chain, zip_longest, tee

fc = # Path to feature class or name of feature layer
flds = # Fields to include in cursor

# Example 1a: Read-only, look-ahead using search cursor & itertools chain, izip, tee
with arcpy.da.SearchCursor(fc, flds) as cur:
    n, n1 = tee(cur)
    n1 = chain(n1, (next(n1),))
    for n_row, n_1row in zip(n, n1):
        print(n_row, n_1row)  

# Example 1b: Read-only, look-ahead using search cursor & itertools izip_longest, tee
with arcpy.da.SearchCursor(fc, flds) as cur:
    n, n1 = tee(cur)
    filler_row = next(n1)
    for n_row, n_1row in zip_longest(n, n1, fillvalue=filler_row):
        print(n_row, n_1row)

# Example 2: Look-ahead using search cursor and nested update cursor
#            & itertools izip_longest
with arcpy.da.SearchCursor(fc, flds) as n1_cur:
    with arcpy.da.UpdateCursor(fc, flds) as n_cur:
        filler_row = next(n1_cur)
        for n_row, n1_row in zip_longest(n_cur, n1_cur, fillvalue=filler_row):
            print(n_row, n1_row)

#