import shelve

s = shelve.open('test_shelf.db')
try:
  s['key1'] = { 'int': 10, 'float':9.5, 'string':'Sample data' }
finally:
  s.close()

import shelve

s = shelve.open('test_shelf.db')
try:
  existing = s['key1']
finally:
  s.close()

print existing

$ python shelve_create.py
$ python shelve_existing.py

{'int': 10, 'float': 9.5, 'string': 'Sample data'}
 

import shelve

s = shelve.open('test_shelf.db', flag='r')
try:
  existing = s['key1']
finally:
  s.close()

print existing

import shelve

s = shelve.open('test_shelf.db')
try:
  print s['key1']
  s['key1']['new_value'] = 'this was not here before'
finally:
  s.close()

s = shelve.open('test_shelf.db', writeback=True)
try:
  print s['key1']
finally:
  s.close()

$ python shelve_create.py
$ python shelve_withoutwriteback.py

{'int': 10, 'float': 9.5, 'string': 'Sample data'}
{'int': 10, 'float': 9.5, 'string': 'Sample data'}
 

import shelve

s = shelve.open('test_shelf.db', writeback=True)
try:
  print s['key1']
  s['key1']['new_value'] = 'this was not here before'
  print s['key1']
finally:
  s.close()

s = shelve.open('test_shelf.db', writeback=True)
try:
  print s['key1']
finally:
  s.close()

 $ python shelve_create.py
$ python shelve_writeback.py
 
{'int': 10, 'float': 9.5, 'string': 'Sample data'}
{'int': 10, 'new_value': 'this was not here before', 'float': 9.5, 'string': 'Sample data'}
 {'int': 10, 'new_value': 'this was not here before', 'float': 9.5, 'string': 'Sample data'}

#!/bin/env python

import time
import datetime
import md5
import shelve

LOGIN_TIME_OUT = 60
db = shelve.open('user_shelve.db', writeback=True)

def newuser():
  global db
  prompt = "login desired: "
  while True:
    name = raw_input(prompt)
    if name in db:
      prompt = "name taken, try another: "
      continue
    elif len(name) == 0:
      prompt = "name should not be empty, try another: "
      continue
    else:
      break
  pwd = raw_input("password: ")
  db[name] = {"password": md5_digest(pwd), "last_login_time": time.time()}
  #print '-->', db

def olduser():
  global db
  name = raw_input("login: ")
  pwd = raw_input("password: ")
  try:
    password = db.get(name).get('password')
  except AttributeError, e:
    print "\033[1;31;40mUsername '%s' doesn't existed\033[0m" % name
    return
  if md5_digest(pwd) == password:
    login_time = time.time()
    last_login_time = db.get(name).get('last_login_time')
    if login_time - last_login_time < LOGIN_TIME_OUT:
      print "\033[1;31;40mYou already logged in at: <%s>\033[0m" % datetime.datetime.fromtimestamp(last_login_time).isoformat()

    db[name]['last_login_time'] = login_time
    print "\033[1;32;40mwelcome back\033[0m", name
  else:
    print "\033[1;31;40mlogin incorrect\033[0m"

def md5_digest(plain_pass):
  return md5.new(plain_pass).hexdigest()

def showmenu():
  #print '>>>', db
  global db
  prompt = """
(N)ew User Login
(E)xisting User Login
(Q)uit
Enter choice: """
  done = False
  while not done:
    chosen = False
    while not chosen:
      try:
        choice = raw_input(prompt).strip()[0].lower()
      except (EOFError, KeyboardInterrupt):
        choice = "q"
      print "\nYou picked: [%s]" % choice
      if choice not in "neq":
        print "invalid option, try again"
      else:
        chosen = True

    if choice == "q": done = True
    if choice == "n": newuser()
    if choice == "e": olduser()
  db.close()

if __name__ == "__main__":
  showmenu()