5597l4

Listing 4. Needs caption

>>> langs = ['c', 'perl', 'tcl/tk']
>>> langIter =iter(langs)
>>> langs.append('c++')
>>> langIter.next()
'c'
>>> langIter.next()
'perl'
>>> langIter.next()
'tcl/tk'
>>> langs
['c', 'perl', 'tcl/tk', 'c++']
>>> langIter.next()                     # added after iter obj created
'c++'
>>> langs.remove('perl')
>>> langs.append('ruby')
>>> langs
['c', 'tcl/tk', 'c++', 'ruby']
>>> langIter.next()                     # out of elements
Traceback (most recent call last):
  File "", line 1, in ?
    langIter.next()
StopIteration
>>> langs.append('java')                # added item to tail
>>> langIter.next()                     # resume iteration
'java'