connected_components lists islands. A missing road splits Kenya in the toy map.

Goal

Print components before and after adding Nakuru—Kisumu.

import networkx as nx
G = nx.Graph([('Nairobi', 'Nakuru'), ('Mombasa', 'Kisumu')])
print([sorted(c) for c in nx.connected_components(G)])

import networkx as nx
G = nx.Graph([('Nairobi', 'Nakuru'), ('Mombasa', 'Kisumu')])
G.add_edge('Nakuru', 'Kisumu')
print(nx.number_connected_components(G))

import networkx as nx
print(nx.is_connected(nx.path_graph(3)))

import networkx as nx
D = nx.DiGraph([('a', 'b'), ('b', 'c')])
print(list(nx.weakly_connected_components(D)))