Python中dictionary items()系列函数的用法实例

import html  # available only in Python 3.x 
def make_elements(name, value, **attrs): 
  keyvals = [' %s="%s"' % item for item in attrs.items()] 
  attr_str = ''.join(keyvals) 
  element = '<{name}{attrs}>{value}</{name}>'.format( 
      name = name, 
      attrs = attr_str, 
      value = html.escape(value)) 
  return element 
make_elements('item', 'Albatross', size='large', quantity=6) 
make_elements('p', '<spam>') 

>>> d = {'size': 'large', 'quantity': 6} 
>>> d.items() 
[('quantity', 6), ('size', 'large')] 

Python 2.7.3 (default, Feb 27 2014, 19:58:35)  
[GCC 4.6.3] on linux2 
Type "help", "copyright", "credits" or "license" for more information. 
>>> d = {'size': 'large', 'quantity': 6} 
>>> il = d.items() 
>>> it = d.iteritems() 
>>> vi = d.viewitems() 
>>> il 
[('quantity', 6), ('size', 'large')] 
>>> it 
<dictionary-itemiterator object at 0x7fe555159f18> 
>>> vi 
dict_items([('quantity', 6), ('size', 'large')]) 

Python 3.4.1 (default, Aug 12 2014, 16:43:01)  
[GCC 4.9.0] on linux 
Type "help", "copyright", "credits" or "license" for more information. 
>>> d = {'size': 'large', 'quantity': 6} 
>>> il = d.items() 
>>> it = d.iteritems() 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
AttributeError: 'dict' object has no attribute 'iteritems' 
>>> vi = d.viewitems() 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
AttributeError: 'dict' object has no attribute 'viewitems' 
>>> il 
dict_items([('size', 'large'), ('quantity', 6)]) 

>>> for k, v in it: 
...  print k, v 
...  
quantity 6 
size large 
>>> for k, v in vi: 
...  print k, v 
...  
quantity 6 
size large 

>>> it = d.iteritems() 
>>> vi = d.viewitems() 
>>> d['newkey'] = 'newvalue' 
>>> d 
{'newkey': 'newvalue', 'quantity': 6, 'size': 'large'} 
>>> vi 
dict_items([('newkey', 'newvalue'), ('quantity', 6), ('size', 'large')]) 
>>> it 
<dictionary-itemiterator object at 0x7f50ab898f70> 
>>> for k, v in vi: 
...  print k, v 
...  
newkey newvalue 
quantity 6 
size large 
>>> for k, v in it: 
...  print k, v 
...  
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
RuntimeError: dictionary changed size during iteration