How to do point-to-point near analysis conditional on common attributes of the two layers in Arcgis 10.2 (advanced)

Question

I am measuring the closest straight distance from cities of interest (in a layer) to their capital cities (in another layer). Basically, distance between a city and a capital city is calculated if only if their country codes are identical. Arcgis license is advanced.

Solution:

The following solution is based on @dklassen. Modification has been made so that I can loop a list of numerical number.

import arcpy
ctryID = [row.ID_0 for row in arcpy.SearchCursor(countryID_feature_class)]
arcpy.MakeFeatureLayer_management('PATH_TO_CITIES_FC','cityfc')
arcpy.MakeFeatureLayer_management('PATH_TO_CAPITALS_FC','capitalfc')

for grd in ctryID:
    arcpy.SelectLayerByAttribute_management('cityfc','NEW_SELECTION',""""ID_0" = {}""".format(grd))
    arcpy.SelectLayerByAttribute_management('capitalfc','NEW_SELECTION',""""ID_0" = {}""".format(grd))
    arcpy.Near_analysis('cityfc','capitalfc',"#","NO_LOCATION","NO_ANGLE")
    arcpy.CopyFeatures_management("cityfc", "c:/temp/ctry{}".format(grd))

arcpy.CreateFeatureclass_management("c:/temp/", "ctryall.shp", "POINT", "c:/temp/ctry1.shp", "DISABLED", "DISABLED")

for grd in ctryID:
    arcpy.Append_management("c:/temp/ctry{}.shp".format(grd), "c:/temp/ctryall.shp")
    arcpy.Delete_management("c:/temp/ctry{}.shp".format(grd))

Answer 1

What you could do is within a loop - create feature layers out of your points - then do the point near analysis. As a brief example:

import arcpy
countries = ['CANADA','USA']
arcpy.MakeFeatureLayer_management('PATH_TO_CITIES_FC','cityfc')
arcpy.MakeFeatureLayer_management('PATH_TO_CAPITALS_FC','capitalfc')

for country in countries:
    arcpy.SelectLayerByAttribute_management('cityfc','NEW_SELECTION',"COUNTRYNAME = '" + str(country) + "'")
    arcpy.SelectLayerByAttribute_management('capitalfc','NEW_SELECTION',"COUNTRYNAME = '" + str(country) + "'")
    # DO POINT NEAR ANALYSIS HERE ON THE 2 Feature Layers

Also if you don't want to type out the list of countries - you could do something like this:

countries = [row.COUNTRYNAME for row in arcpy.SearchCursor(country_feature_class)]