python 自制文件存储数据库

make_db_file.py
"""
 Save in-memory database object to a file with custom formatting;
 assume 'endrec.', 'enddb.', and '=>' are not used in the data;
 assume db is dict of dict;  warning: eval can be dangerous - it
 runs strings as code;  could also eval() record dict all at once;
 could also dbfile.write(key + '\n') vs print(key, file=dbfile);
 """
dbfilename = 'people-file'
 ENDDB  = 'enddb.'
 ENDREC = 'endrec.'
 RECSEP = '=>'
def storeDbase(db, dbfilename=dbfilename):
 "formatted dump of database to flat file"
 dbfile = open(dbfilename, 'w')
 for key in db:
 print(key, file=dbfile)
 for (name, value) in db[key].items():
 print(name + RECSEP + repr(value), file=dbfile)
 print(ENDREC, file=dbfile)
 print(ENDDB, file=dbfile)
 dbfile.close()
def loadDbase(dbfilename=dbfilename):
 "parse data to reconstruct database"
 dbfile = open(dbfilename)
 import sys
 sys.stdin = dbfile
 db = {}
 key = input()
 while key != ENDDB:
 rec = {}
 field = input()
 while field != ENDREC:
 name, value = field.split(RECSEP)
 rec[name] = eval(value)
 field = input()
 db[key] = rec
 key = input()
 return db
if name == 'main':
 from initdata import db
 storeDbase(db)

###############people-file
 bob
 pay=>30000
 job=>'dev'
 age=>42
 name=>'Bob Smith'
 endrec.
 sue
 pay=>44000.0
 job=>'hdw'
 age=>45
 name=>'Sue Jones'
 endrec.
 tom
 pay=>0
 job=>None
 age=>50
 name=>'Tom Tom'
 endrec.
 enddb.

from make_db_file import loadDbase
 db = loadDbase()
 for key in db:
 print(key, '=>\n  ', db[key])
 print(db['sue']['name'])

from make_db_file import loadDbase, storeDbase
 db = loadDbase()
 db['sue']['pay'] *= 1.10
 db['tom']['name'] = 'Tom Tom'
 storeDbase(db)