Usage of python pickles and shelve modules

1. The pickle

    Write: opens a file descriptor in write mode and calls pickle.dump to write the object in

    dn = {'baidu':'www.baidu.com','qq':'www.qq.com','360':'www.360.cn'}
    name = ['mayun','mahuateng','liyanhong']
    f = open(r'C:a.txt','w')
    pickle.dump(dn,f)      ## Write an object 
    pickle.dump(name,f)  ## Write another object 
    f.close()  
    Read: opens the file descriptor as read, calling pickle.load Load the object 
    f = open(r'C:a.txt')
    pickle.load(f)             ## Load an object 
    pickle.load(f)             ## Load another object 
    f.close()

    The shelve module is simpler than the pickle module, with only an open function that returns a dictionary-like object that can be read and written

   f = shelve.open(r'C:b.txt')
   f  ## Return empty dictionary 
   f['baidu'] = 'www.baidu.com'
   f['qq'] = 'www.qq.com'
   f['360'] = 'www.360.cn'
   f  ## Return a dictionary 
   f.close()
   f = shelve.open(r'C:b.txt')
   f ## Return a dictionary f