CODEWITHSUNDEEP
pythonpython-3.x
user9713961
user9713961

Reputation:

Searching for a set, within a tuple

The tuple G contains the set of edges, the set of vertices, and the weight of the edges. 

#Weighted Graph
G = [['a', 'b' , 'c' , 'd']
     [({'a', 'b'}, 4), ({'a', 'c'}, 6), ({'a', 'd'}, 8)]

I am trying to return the weight of an edge, given an edge. For example, for the edge {'a', 'b'}, I am trying to return the value 4. Is it possible to search for {'a', 'b'} and return this value?

Upvotes: 1

Views: 111

Answers (2)

DAkbariSE
DAkbariSE

Reputation: 133

you can store start and end point of each edge in two tuples: E1 and E2. additionally you may store weight of each edge into tuple W and search for appropriate edge by iterating through elements of E1 and E2 finally you can access to appropriate weight by using W tuple. 

G = ('a', 'b', 'c', 'd')

E1 = ('a', 'a', 'a')
E2 = ('b', 'c', 'd')
W = (4, 6, 8)

for i in range(len(E1)):
    if E1[i] == 'a' and E2[i] == 'b':
        print(W[i])

Upvotes: 0

Kasravnd
Kasravnd

Reputation: 107287

You can do that by looping over the second list inside G but basically list is not a proper data structure for representing a graph. As a more optimized and Pythonic way you can preserve them in a dictionary and access to each edge using a simple indexing. There's one thing you should note though. sets are not hashable and you have to use tuple or another hashable iterator like frozenset for preserving your edges as the dictionary keys.

In [20]: nodes, edges = G[0], {tuple(i): j for i, j in G[1]}

In [21]: edges
Out[21]: {('a', 'b'): 4, ('a', 'c'): 6, ('a', 'd'): 8}

In [22]: edges[('a', 'b')]
Out[22]: 4

Note that here I'm converting your current data to a dictionary but if you are generating this data by yourself it's better to do this at that level and create a dictionary at the first place before creating a nested list like this.

Upvotes: 2

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