back-edge-detection.py

import networkx as nx
from sqlalchemy import create_engine, MetaData
import sqlalchemy

engine = create_engine('mysql+mysqldb://........', echo=True)

meta = MetaData()
meta.reflect(bind=engine)
try:
  # Topological sort, which will yield an exception if there is a cyclical dependency
  meta.sorted_tables
except sqlalchemy.exc.CircularDependencyError as e:
  G=nx.DiGraph()
  cycle_tables = set([t.name for t in e.cycles])

  for t in e.cycles:
    for fk in t.foreign_keys:
      table, col = fk.target_fullname.split('.')
      if (table in cycle_tables): # Skip any foreign keys that aren't a part of the cycle tables
        G.add_edge(t.name, table)
      
  agraph = nx.to_agraph(G)
  agraph.draw('graph.png', format='png', prog='dot')
else:
  print("There are no cyclical depenencies in the database")