chapter_15.1.py

import sqlite3

conn = sqlite3.connect('emaildb.sqlite')
cur = conn.cursor()

cur.execute('DROP TABLE IF EXISTS Counts')

cur.execute('''
CREATE TABLE Counts (org TEXT, count INTEGER)''')

fname = 'mbox.txt'
fh = open(fname)
for line in fh:
    if not line.startswith ('From:'): continue
    pieces = line.split()
    email = pieces[1]
    dom = email.split('@')
    dname = dom[1]
    cur.execute('SELECT count FROM Counts WHERE org = ? ',(dname,))
    row = cur.fetchone()
    if row is None:
        cur.execute(''' INSERT INTO Counts (org,count)
                    VALUES (?,1)''',(dname,))
    else:
        cur.execute('UPDATE Counts SET count = count + 1 WHERE org = ?', (dname,))

conn.commit()
sqlstr = 'SELECT org, count FROM Counts ORDER BY count'

for row in cur.execute(sqlstr):
    print(str(row[0]), row[1])

cur.close()