Anki Books

How does Anki Books create Anki notes?

Knowledge graphs in Anki Books

The Anki Books data can be downloaded as CSV files for study with network analysis tools like NetworkX and Gephi. The data structure is largely a tree which would not be interesting on its own, but there is a non-trivial structure due to the cloze deletion notes (fill-in-the-blank flashcards). Each fill-in-the-blank becomes a concept. A cloze deletion note with multiple concepts is a node with an edge to each concept. Visualization of the knowledge structure is a fun way to track your Anki learning habits and it is also useful to see what ideas have been studied from multiple sources. It is especially satisfying because studying the represented information with spaced repetition encodes and consolidates it into long-term memory. Memory naturally has an associative nature, and the mental representation overlaps with the physical representation in the database.

Incremental reading in Anki Books

How does Anki Books create graphs?

// Programmer #1:
// Sorry about the font on this code
// TODO: fix font
// Programmer #2:
// Leave this comment as a warning to be wary in the code around here
import networkx as nx
import matplotlib.pyplot as plt
import csv

path = "./prod"

G = nx.Graph()

G.add_node("center")

with open(f"{path}/books.csv", "r") as file:
  csvreader = csv.reader(file)
  next(csvreader, None)
  for row in csvreader:
    node_id = row[0]
    title = row[1]
    parent_book_id = row[2]
    G.add_node(node_id)
    G.nodes[node_id]["book"] = True
    G.nodes[node_id]["title"] = title
    if parent_book_id != "":
      G.add_edge(node_id, parent_book_id)
    else:
      G.add_edge(node_id, "center")

with open(f"{path}/articles.csv", "r") as file:
  csvreader = csv.reader(file)
  next(csvreader, None)
  for row in csvreader:
    node_id = row[0]
    title = row[1]
    book_id = row[2]
    G.add_node(node_id)
    G.nodes[node_id]["article"] = True
    G.nodes[node_id]["title"] = title
    G.add_edge(node_id, book_id)

with open(f"{path}/basic_notes.csv", 'r') as file:
  csvreader = csv.reader(file)
  next(csvreader, None)
  for row in csvreader:
    node_id = row[0]
    front = row[1]
    back = row[2]
    article_id = row[3]
    G.add_node(node_id)
    G.nodes[node_id]["basic_note"] = True
    G.nodes[node_id]["front"] = front
    G.nodes[node_id]["back"] = back
    G.add_edge(node_id, article_id)

with open(f"{path}/concepts.csv", "r") as file:
  csvreader = csv.reader(file)
  next(csvreader, None)
  for row in csvreader:
    node_id = row[0]
    name = row[1]
    G.add_node(node_id)
    G.nodes[node_id]["name"] = name

with open(f"{path}/cloze_notes.csv", "r") as file:
  csvreader = csv.reader(file)
  next(csvreader, None)
  for row in csvreader:
    node_id = row[0]
    sentence = row[1]
    article_id = row[2]
    G.add_node(node_id)
    G.nodes[node_id]["sentence"] = sentence
    G.add_edge(node_id, article_id)

with open(f"{path}/cloze_notes_concepts.csv", "r") as file:
  csvreader = csv.reader(file)
  next(csvreader, None)
  for row in csvreader:
    cloze_note_id = row[0]
    concept_id = row[1]
    G.add_edge(cloze_note_id, concept_id)

nx.draw_networkx(G, with_labels=False, node_size=5)
plt.savefig(f"{path}/basic_notes_graph.svg")
nx.write_graphml(G, f"{path}/basic_notes_graph.graphml")

Example: a small area of an Anki Books graph

Why does Anki Books use Ruby on Rails?

Why does Anki Books use PostgreSQL?

PostgreSQL is (one of) the finest and most advanced free and open-source object-relational database management software in the world.

Example: an Anki Books article

ABC metric

##
# Returns nth number in the Fibonacci sequence starting with 1, 1 ...
def fibonacci(n)
  [1, 2].include?(n) ? 1 : fibonacci(n - 1) + fibonacci(n - 2)
end

5.times do |i|
  puts fibonacci(i + 1)
end

Cyclomatic complexity

def triangle(a, b, c)
  if invalid_triangle?(a, b, c)
    :invalid
  elsif a == b && b == c && a == c
    :equilateral
  elsif a == b || b == c || a == c
    :isosceles
  else
    :scalene
  end
end

The algorithm counts decision points and adds one.

An if statement (or unless or ?:) increases the complexity by one. An else branch does not, since it doesn’t add a decision point. The && operator (or keyword and) can be converted to a nested if statement, and ||/or is shorthand for a sequence of ifs, so they also add one. Loops can be said to have an exit condition, so they add one.

The Law of Demeter