Basic Graph Representation in Python

Adjacency Dicts With Edge Weights

a, b, c, d, e, f, g, h = range(8)

N = [
    {b:2, c:1, d:3, e:9, f:4},
    {c:4, e:3},
    {d:8},
    {e:7},
    {f:5},
    {c:2, g:2, h:2},
    {f:1, h:6},
    {f:9, g:8}
]

b in N[a] # N[a] is the neighbours of a
len(N[f]) # Degree
N[a][b] #Edge weight for (a, b)

Adjacency List

# Time is O(n)
a, b, c, d, e, f, g, h = range(8)

N = [
    [b, c, d, e, f],
    [c, e],
    [d],
    [e],
    [f],
    [c, g, h],
    [f, h],
    [f, g]
]

b in N[a] # N[a] is the neighbours of a 

Adjacency Set

a, b, c, d, e, f, g, h = range(8)

N = [
    {b, c, d, e, f},
    {c, e},
    {d},
    {e},
    {f},
    {c, g, h},
    {f, h},
    {f, g}
]

b in N[a] # N[a] is the neighbours of a

Adjacency Sets

a, b, c, d, e, f, g, h = range(8)

N = {
    'a': set('bcdef'),
    'b': set('ce'),
    'c': set('d'),
    'd': set('e'),
    'e': set('f'),
    'f': set('cgh'),
    'g': set('fh'),
    'h': set('fg')
}

b in N[a] # N[a] is the neighbours of a