Generate table of intersecting lines for the same feature class

Question

I have a Polyline feature class. For each feature in the Fc...I want the list of all the connecting lines(A table). For Example For Feature 17686 Connecting Id are : 17688 & 17684. For Reference :

Answer 1

Derive lines end points, delete spatially identical, name points and transfer their attributes to lines table:

Export lines table to 2 identical stand-alone table in GDB, e.g. ABC and CBA and Make Query Table No1:

Repeat to create Query Table No2 and 3, using:

ABC.ton = BCA.fromn
and
ABC.ton = BCA.ton

You'll need to export all query tables and concatenate them. Table below shows all lines connected to line 612, compare it with 1st picture:

This hectic workflow can be replaced by tiny field calculator expression:

import collections
from collections import defaultdict
dF,dT=defaultdict(list),defaultdict(list)
tbl=arcpy.da.TableToNumPyArray("LINKS",("LINKNO" , "fromn" , "ton"))
for i,f,t in tbl:
 dF[f]+=[str(i)]; dF[t]+=[str(i)]
 dT[t]+=[str(i)]; dT[f]+=[str(i)]

def getConnected(i,f,t):
 bigList = set(dF[f]+dT[t])
 bigList.remove(str(i))
 return ','.join(list(bigList))
#-----
getConnected( !LINKNO!, !fromn! , !ton! )

Use python, I think there is a need for one more query table if there are more than one line going out from FromNode:(