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72 changes: 72 additions & 0 deletions Graphs/pagerank.py
Original file line number Diff line number Diff line change
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'''
Author: https://github.com/bhushan-borole
'''
'''
The input graph for the algorithm is:

A B C
A 0 1 1
B 0 0 1
C 1 0 0

'''

graph = [[0, 1, 1],
[0, 0, 1],
[1, 0, 0]]


class Node:
def __init__(self, name):
self.name = name
self.inbound = []
self.outbound = []

def add_inbound(self, node):
self.inbound.append(node)

def add_outbound(self, node):
self.outbound.append(node)

def __repr__(self):
return 'Node {}: Inbound: {} ; Outbound: {}'.format(self.name,
self.inbound,
self.outbound)


def page_rank(nodes, limit=3, d=0.85):
ranks = {}
for node in nodes:
ranks[node.name] = 1

outbounds = {}
for node in nodes:
outbounds[node.name] = len(node.outbound)

for i in range(limit):
print("======= Iteration {} =======".format(i+1))
for j, node in enumerate(nodes):
ranks[node.name] = (1 - d) + d * sum([ ranks[ib]/outbounds[ib] for ib in node.inbound ])
print(ranks)


def main():
names = list(input('Enter Names of the Nodes: ').split())

nodes = [Node(name) for name in names]

for ri, row in enumerate(graph):
for ci, col in enumerate(row):
if col == 1:
nodes[ci].add_inbound(names[ri])
nodes[ri].add_outbound(names[ci])

print("======= Nodes =======")
for node in nodes:
print(node)

page_rank(nodes)


if __name__ == '__main__':
main()