ID1        ID2
20         2445
22         2557
23         2456

import pandas
import arcpy

all_snapped_nodes = 'all_snapped_nodes.shp'
all_new_nodes = 'AllnewNodes.shp'

new_old_node_conversion = pandas.read_csv('new_old_node_conversion.csv',index_col = 0, header = None)
#more code thats snaps IDs from layer1 to layer2.