How to make a loop for select by attribute?

Question

I am trying to pull out a sample out of a geodatabase file. I have 100800 sample and I need to select 28 records, basically every 3600, I am going to start with FID=0 and go from there. Unfortunately I haven't been able to make it work. this is what I have done so far. anyone can give me a hint, it's gonna be a huge help.

import arcpy, sys, os

Input=sys.argv[1]
field=sys.argv[2]
counts=sys.argv[3]
output=sys.argv[4]

def deleteMe(fc):
    if arcpy.Exists(fc):
        arcpy.Delete_management(fc)
    return fc


cursor =arcpy.da.SearchCursor(Input,field)
for row in cursor:
    a=row[0]
    while row:
        x=a+3600

    arcpy.MakeFeatureLayer_management(Input, deleteMe("lyr"))
    arcpy.SelectLayerByAttribute_management ("lyr", "NEW_SELECTION",a)

#arcpy.SelectLayerByAttribute_management ("lyr", "ADD_TO_SELECTION",x)



arcpy.CopyFeatures_management ("lyr", deleteMe(output))

Answer 1

How about just making a list of the OBJECTID's you want and making it into a query?

## start with list of all objectids
all_oids = [row[0] for row in arcpy.da.SearchCursor(Input,"OBJECTID")]

## make list of every 3600th objectid
oids = []
for index, oid in enumerate(range(len(all_oids))):
    if index % 3600 == 0:
        oids.append(oid)

## make sql query
qry = '"OBJECTID" IN ({0})'.format(".join(oids))

## deal with the datasets
arcpy.MakeFeatureLayer_management(Input, deleteMe("lyr"))
arcpy.SelectLayerByAttribute_management ("lyr", "NEW_SELECTION", qry)
arcpy.CopyFeatures_management ("lyr", deleteMe(output))

Enumerate is a super useful function. It iterates a list and also returns the index of each item. You're using it here to run through the list of OBJECTIDs and if the index is a factor of 3600 the oid appended to a list. Then use that list to create a query that you can apply to the feature layer.