NetWorkx Module

I use the NetWorkx module to find all the shortest strings between two points of a graph.

Everything works well at a close detail; as soon as there are no paths between two points, my script stops and does not work for the other couples (starting point, point of arrival).

So I want to know how to add a condition so that when there are no paths between two points, I print the following message "No way between these two points" and continue with other couples

Here is my code:

import networkx as nx from collections import defaultdict dd=defaultdict(set) P=[]

File content all couples (starting point, end point) to test

with open("3080_interactions_pour_736.txt","r") as f0: for lignes0 in f0: lignes0=lignes0.rstrip('\n').split(" ") prot1=lignes0[0] prot2=lignes0[1] couple=prot1,prot2 P.append(list(couple)) #print(P)

File containing all the binary interactions composing my graph

with open("736(int_connues_avec_scores_sup_0).txt","r") as f1: for lignes in f1: if lignes.startswith('9606'): lignes=lignes.rstrip('\n').split(" ") proteine1=lignes[2] proteine2=lignes[3] dd[proteine1].add(proteine2)

For every couple of my first file, I apply the module of the shortest chains:

for couples in P: prot1=couples[0] prot2=couples[1] Lchaines=([p for p in nx.all_shortest_paths(dd, source=prot1, target=prot2, weight=None)]) print("") print("The first protein in the chain is", prot1) print("The last protein in the chain is", prot2) print("") print("Minimal size chain(s):") print("")

for chaines in Lchaines:

    #To have chains of size 11 maximum
    if len(chaines) <= 11:

        print(' '.join(chaines))
    else :

        print('ERROR - The minimum size of the chains exceeds the limit')
        break
print("")
print("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx")

Here is the error message I receive:

Traceback (most recent call last):

File "C:\Users\loisv\Desktop\pluscourtchemin.py", line 26, in

Lchaines=([p for p in nx.all_shortest_paths(dd, source=prot1, target=prot2, weight=None)])

File "C:\Users\loisv\Desktop\pluscourtchemin.py", line 26, in

Lchaines=([p for p in nx.all_shortest_paths(dd, source=prot1, target=prot2, weight=None)])

File "C:\Users\loisv\AppData\Local\Programs\Python\Python37-32\lib\site-packages\networkx\algorithms\shortest_paths\generic.py", line 481, in all_shortest_paths

'from Source {}'.format(target, source))

networkx.exception.NetworkXNoPath: Target IKBKE cannot be reachedfrom Source LCK

Thanks for your help :)