pagerank

pagerank.py

from __future__ import annotations

class Page:
    o = 0.5

    def __init__(self, iid):
        self.id = iid
        self.references = []
        self.referers = []
        self.rank = 1

    def __repr__(self):
        return f"<Page {self.id} references={len(self.references)}, referers={len(self.referers)}>"

    def add_reference(self, page: Page):
        if page not in self.references:
            self.references.append(page)
            page.add_referer(self)

    def add_referer(self, page: Page):
        if page not in self.referers:
            self.referers.append(page)
            page.add_reference(self)

    def rank_impl(self):
        k = 0
        for x in self.referers:
            k += x.rank / len(x.references)

        b = (1 - self.o) + self.o * k

        return b

    def calculate_rank(self, iterations):
        if iterations > 0:
            v = {}

            # calculate the rank
            for x in self.referers:
                v[x.id] = x.calculate_rank(iterations-1)

            # apply the rank later so we don't end up causing false results
            for x in self.referers:
                x.rank = v[x.id]

        return round(self.rank_impl(), 10)



a = Page("a")
b = Page("b")
c = Page("c")

a.add_reference(b)
a.add_reference(c)

b.add_reference(c)

c.add_reference(a)

for x in range(10):
    a.rank = 1
    b.rank = 1
    c.rank = 1

    print(x, c.calculate_rank(x))