python的基础类源码解析——collection类

1、计数器（counter）

Counter是对字典类型的补充，用于追踪值的出现次数。

ps：具备字典的所有功能 + 自己的功能

 ########################################################################
 ###  Counter
 ########################################################################

 class Counter(dict):
     '''Dict subclass for counting hashable items.  Sometimes called a bag
     or multiset.  Elements are stored as dictionary keys and their counts
     are stored as dictionary values.

     >>> c = Counter('abcdeabcdabcaba')  # count elements from a string

     >>> c.most_common(3)                # three most common elements
     [('a', 5), ('b', 4), ('c', 3)]
     >>> sorted(c)                       # list all unique elements
     ['a', 'b', 'c', 'd', 'e']
     >>> ''.join(sorted(c.elements()))   # list elements with repetitions
     'aaaaabbbbcccdde'
     >>> sum(c.values())                 # total of all counts

     >>> c['a']                          # count of letter 'a'
     >>> for elem in 'shazam':           # update counts from an iterable
     ...     c[elem] += 1                # by adding 1 to each element's count
     >>> c['a']                          # now there are seven 'a'
     >>> del c['b']                      # remove all 'b'
     >>> c['b']                          # now there are zero 'b'

     >>> d = Counter('simsalabim')       # make another counter
     >>> c.update(d)                     # add in the second counter
     >>> c['a']                          # now there are nine 'a'

     >>> c.clear()                       # empty the counter
     >>> c
     Counter()

     Note:  If a count is set to zero or reduced to zero, it will remain
     in the counter until the entry is deleted or the counter is cleared:

     >>> c = Counter('aaabbc')
     >>> c['b'] -= 2                     # reduce the count of 'b' by two
     >>> c.most_common()                 # 'b' is still in, but its count is zero
     [('a', 3), ('c', 1), ('b', 0)]

     '''
     # References:
     #   http://en.wikipedia.org/wiki/Multiset
     #   http://www.gnu.org/software/smalltalk/manual-base/html_node/Bag.html
     #   http://www.demo2s.com/Tutorial/Cpp/0380__set-multiset/Catalog0380__set-multiset.htm
     #   http://code.activestate.com/recipes/259174/
     #   Knuth, TAOCP Vol. II section 4.6.3

     def __init__(self, iterable=None, **kwds):
         '''Create a new, empty Counter object.  And if given, count elements
         from an input iterable.  Or, initialize the count from another mapping
         of elements to their counts.

         >>> c = Counter()                           # a new, empty counter
         >>> c = Counter('gallahad')                 # a new counter from an iterable
         >>> c = Counter({'a': 4, 'b': 2})           # a new counter from a mapping
         >>> c = Counter(a=4, b=2)                   # a new counter from keyword args

         '''
         super(Counter, self).__init__()
         self.update(iterable, **kwds)

     def __missing__(self, key):
         """ 对于不存在的元素，返回计数器为0 """
         'The count of elements not in the Counter is zero.'
         # Needed so that self[missing_item] does not raise KeyError
         return 0

     def most_common(self, n=None):
         """ 数量大于等n的所有元素和计数器 """
         '''List the n most common elements and their counts from the most
         common to the least.  If n is None, then list all element counts.

         >>> Counter('abcdeabcdabcaba').most_common(3)
         [('a', 5), ('b', 4), ('c', 3)]

         '''
         # Emulate Bag.sortedByCount from Smalltalk
         if n is None:
             return sorted(self.iteritems(), key=_itemgetter(1), reverse=True)
         return _heapq.nlargest(n, self.iteritems(), key=_itemgetter(1))

     def elements(self):
         """ 计数器中的所有元素，注：此处非所有元素集合，而是包含所有元素集合的迭代器 """
         '''Iterator over elements repeating each as many times as its count.

         >>> c = Counter('ABCABC')
         >>> sorted(c.elements())
         ['A', 'A', 'B', 'B', 'C', 'C']

         # Knuth's example for prime factors of 1836:  2**2 * 3**3 * 17**1
         >>> prime_factors = Counter({2: 2, 3: 3, 17: 1})
         >>> product = 1
         >>> for factor in prime_factors.elements():     # loop over factors
         ...     product *= factor                       # and multiply them
         >>> product

         Note, if an element's count has been set to zero or is a negative
         number, elements() will ignore it.

         '''
         # Emulate Bag.do from Smalltalk and Multiset.begin from C++.
         return _chain.from_iterable(_starmap(_repeat, self.iteritems()))

     # Override dict methods where necessary

     @classmethod
     def fromkeys(cls, iterable, v=None):
         # There is no equivalent method for counters because setting v=1
         # means that no element can have a count greater than one.
         raise NotImplementedError(
             'Counter.fromkeys() is undefined.  Use Counter(iterable) instead.')

     def update(self, iterable=None, **kwds):
         """ 更新计数器，其实就是增加；如果原来没有，则新建，如果有则加一 """
         '''Like dict.update() but add counts instead of replacing them.

         Source can be an iterable, a dictionary, or another Counter instance.

         >>> c = Counter('which')
         >>> c.update('witch')           # add elements from another iterable
         >>> d = Counter('watch')
         >>> c.update(d)                 # add elements from another counter
         >>> c['h']                      # four 'h' in which, witch, and watch

         '''
         # The regular dict.update() operation makes no sense here because the
         # replace behavior results in the some of original untouched counts
         # being mixed-in with all of the other counts for a mismash that
         # doesn't have a straight-forward interpretation in most counting
         # contexts.  Instead, we implement straight-addition.  Both the inputs
         # and outputs are allowed to contain zero and negative counts.

         if iterable is not None:
             if isinstance(iterable, Mapping):
                 if self:
                     self_get = self.get
                     for elem, count in iterable.iteritems():
                         self[elem] = self_get(elem, 0) + count
                 else:
                     super(Counter, self).update(iterable) # fast path when counter is empty
             else:
                 self_get = self.get
                 for elem in iterable:
                     self[elem] = self_get(elem, 0) + 1
         if kwds:
             self.update(kwds)

     def subtract(self, iterable=None, **kwds):
         """ 相减，原来的计数器中的每一个元素的数量减去后添加的元素的数量 """
         '''Like dict.update() but subtracts counts instead of replacing them.
         Counts can be reduced below zero.  Both the inputs and outputs are
         allowed to contain zero and negative counts.

         Source can be an iterable, a dictionary, or another Counter instance.

         >>> c = Counter('which')
         >>> c.subtract('witch')             # subtract elements from another iterable
         >>> c.subtract(Counter('watch'))    # subtract elements from another counter
         >>> c['h']                          # 2 in which, minus 1 in witch, minus 1 in watch
         >>> c['w']                          # 1 in which, minus 1 in witch, minus 1 in watch
         -1

         '''
         if iterable is not None:
             self_get = self.get
             if isinstance(iterable, Mapping):
                 for elem, count in iterable.items():
                     self[elem] = self_get(elem, 0) - count
             else:
                 for elem in iterable:
                     self[elem] = self_get(elem, 0) - 1
         if kwds:
             self.subtract(kwds)

     def copy(self):
         """ 拷贝 """
         'Return a shallow copy.'
         return self.__class__(self)

     def __reduce__(self):
         """ 返回一个元组（类型，元组） """
         return self.__class__, (dict(self),)

     def __delitem__(self, elem):
         """ 删除元素 """
         'Like dict.__delitem__() but does not raise KeyError for missing values.'
         if elem in self:
             super(Counter, self).__delitem__(elem)

     def __repr__(self):
         if not self:
             return '%s()' % self.__class__.__name__
         items = ', '.join(map('%r: %r'.__mod__, self.most_common()))
         return '%s({%s})' % (self.__class__.__name__, items)

     # Multiset-style mathematical operations discussed in:
     #       Knuth TAOCP Volume II section 4.6.3 exercise 19
     #       and at http://en.wikipedia.org/wiki/Multiset
     #
     # Outputs guaranteed to only include positive counts.
     #
     # To strip negative and zero counts, add-in an empty counter:
     #       c += Counter()

     def __add__(self, other):
         '''Add counts from two counters.

         >>> Counter('abbb') + Counter('bcc')
         Counter({'b': 4, 'c': 2, 'a': 1})

         '''
         if not isinstance(other, Counter):
             return NotImplemented
         result = Counter()
         for elem, count in self.items():
             newcount = count + other[elem]
             if newcount > 0:
                 result[elem] = newcount
         for elem, count in other.items():
             if elem not in self and count > 0:
                 result[elem] = count
         return result

     def __sub__(self, other):
         ''' Subtract count, but keep only results with positive counts.

         >>> Counter('abbbc') - Counter('bccd')
         Counter({'b': 2, 'a': 1})

         '''
         if not isinstance(other, Counter):
             return NotImplemented
         result = Counter()
         for elem, count in self.items():
             newcount = count - other[elem]
             if newcount > 0:
                 result[elem] = newcount
         for elem, count in other.items():
             if elem not in self and count < 0:
                 result[elem] = 0 - count
         return result

     def __or__(self, other):
         '''Union is the maximum of value in either of the input counters.

         >>> Counter('abbb') | Counter('bcc')
         Counter({'b': 3, 'c': 2, 'a': 1})

         '''
         if not isinstance(other, Counter):
             return NotImplemented
         result = Counter()
         for elem, count in self.items():
             other_count = other[elem]
             newcount = other_count if count < other_count else count
             if newcount > 0:
                 result[elem] = newcount
         for elem, count in other.items():
             if elem not in self and count > 0:
                 result[elem] = count
         return result

     def __and__(self, other):
         ''' Intersection is the minimum of corresponding counts.

         >>> Counter('abbb') & Counter('bcc')
         Counter({'b': 1})

         '''
         if not isinstance(other, Counter):
             return NotImplemented
         result = Counter()
         for elem, count in self.items():
             other_count = other[elem]
             newcount = count if count < other_count else other_count
             if newcount > 0:
                 result[elem] = newcount
         return result

 Counter

Counter Code

我们从中挑选一些相对常用的方法来举例：

在上面的例子我们可以看出，counter方法返回的是一个字典，它将字符串中出现的所有字符都进行了统计。在这里再介绍一下update方法，这个update方法是将两次统计的结果相加，和字典的update略有不同。

　　

2、有序字典(orderedDict )

orderdDict是对字典类型的补充，他记住了字典元素添加的顺序

 class OrderedDict(dict):
     'Dictionary that remembers insertion order'
     # An inherited dict maps keys to values.
     # The inherited dict provides __getitem__, __len__, __contains__, and get.
     # The remaining methods are order-aware.
     # Big-O running times for all methods are the same as regular dictionaries.

     # The internal self.__map dict maps keys to links in a doubly linked list.
     # The circular doubly linked list starts and ends with a sentinel element.
     # The sentinel element never gets deleted (this simplifies the algorithm).
     # Each link is stored as a list of length three:  [PREV, NEXT, KEY].

     def __init__(self, *args, **kwds):
         '''Initialize an ordered dictionary.  The signature is the same as
         regular dictionaries, but keyword arguments are not recommended because
         their insertion order is arbitrary.

         '''
         if len(args) > 1:
             raise TypeError('expected at most 1 arguments, got %d' % len(args))
         try:
             self.__root
         except AttributeError:
             self.__root = root = []                     # sentinel node
             root[:] = [root, root, None]
             self.__map = {}
         self.__update(*args, **kwds)

     def __setitem__(self, key, value, dict_setitem=dict.__setitem__):
         'od.__setitem__(i, y) <==> od[i]=y'
         # Setting a new item creates a new link at the end of the linked list,
         # and the inherited dictionary is updated with the new key/value pair.
         if key not in self:
             root = self.__root
             last = root[0]
             last[1] = root[0] = self.__map[key] = [last, root, key]
         return dict_setitem(self, key, value)

     def __delitem__(self, key, dict_delitem=dict.__delitem__):
         'od.__delitem__(y) <==> del od[y]'
         # Deleting an existing item uses self.__map to find the link which gets
         # removed by updating the links in the predecessor and successor nodes.
         dict_delitem(self, key)
         link_prev, link_next, _ = self.__map.pop(key)
         link_prev[1] = link_next                        # update link_prev[NEXT]
         link_next[0] = link_prev                        # update link_next[PREV]

     def __iter__(self):
         'od.__iter__() <==> iter(od)'
         # Traverse the linked list in order.
         root = self.__root
         curr = root[1]                                  # start at the first node
         while curr is not root:
             yield curr[2]                               # yield the curr[KEY]
             curr = curr[1]                              # move to next node

     def __reversed__(self):
         'od.__reversed__() <==> reversed(od)'
         # Traverse the linked list in reverse order.
         root = self.__root
         curr = root[0]                                  # start at the last node
         while curr is not root:
             yield curr[2]                               # yield the curr[KEY]
             curr = curr[0]                              # move to previous node

     def clear(self):
         'od.clear() -> None.  Remove all items from od.'
         root = self.__root
         root[:] = [root, root, None]
         self.__map.clear()
         dict.clear(self)

     # -- the following methods do not depend on the internal structure --

     def keys(self):
         'od.keys() -> list of keys in od'
         return list(self)

     def values(self):
         'od.values() -> list of values in od'
         return [self[key] for key in self]

     def items(self):
         'od.items() -> list of (key, value) pairs in od'
         return [(key, self[key]) for key in self]

     def iterkeys(self):
         'od.iterkeys() -> an iterator over the keys in od'
         return iter(self)

     def itervalues(self):
         'od.itervalues -> an iterator over the values in od'
         for k in self:
             yield self[k]

     def iteritems(self):
         'od.iteritems -> an iterator over the (key, value) pairs in od'
         for k in self:
             yield (k, self[k])

     update = MutableMapping.update

     __update = update # let subclasses override update without breaking __init__

     __marker = object()

     def pop(self, key, default=__marker):
         '''od.pop(k[,d]) -> v, remove specified key and return the corresponding
         value.  If key is not found, d is returned if given, otherwise KeyError
         is raised.

         '''
         if key in self:
             result = self[key]
             del self[key]
             return result
         if default is self.__marker:
             raise KeyError(key)
         return default

     def setdefault(self, key, default=None):
         'od.setdefault(k[,d]) -> od.get(k,d), also set od[k]=d if k not in od'
         if key in self:
             return self[key]
         self[key] = default
         return default

     def popitem(self, last=True):
         '''od.popitem() -> (k, v), return and remove a (key, value) pair.
         Pairs are returned in LIFO order if last is true or FIFO order if false.

         '''
         if not self:
             raise KeyError('dictionary is empty')
         key = next(reversed(self) if last else iter(self))
         value = self.pop(key)
         return key, value

     def __repr__(self, _repr_running={}):
         'od.__repr__() <==> repr(od)'
         call_key = id(self), _get_ident()
         if call_key in _repr_running:
             return '...'
         _repr_running[call_key] = 1
         try:
             if not self:
                 return '%s()' % (self.__class__.__name__,)
             return '%s(%r)' % (self.__class__.__name__, self.items())
         finally:
             del _repr_running[call_key]

     def __reduce__(self):
         'Return state information for pickling'
         items = [[k, self[k]] for k in self]
         inst_dict = vars(self).copy()
         for k in vars(OrderedDict()):
             inst_dict.pop(k, None)
         if inst_dict:
             return (self.__class__, (items,), inst_dict)
         return self.__class__, (items,)

     def copy(self):
         'od.copy() -> a shallow copy of od'
         return self.__class__(self)

     @classmethod
     def fromkeys(cls, iterable, value=None):
         '''OD.fromkeys(S[, v]) -> New ordered dictionary with keys from S.
         If not specified, the value defaults to None.

         '''
         self = cls()
         for key in iterable:
             self[key] = value
         return self

     def __eq__(self, other):
         '''od.__eq__(y) <==> od==y.  Comparison to another OD is order-sensitive
         while comparison to a regular mapping is order-insensitive.

         '''
         if isinstance(other, OrderedDict):
             return dict.__eq__(self, other) and all(_imap(_eq, self, other))
         return dict.__eq__(self, other)

     def __ne__(self, other):
         'od.__ne__(y) <==> od!=y'
         return not self == other

     # -- the following methods support python 3.x style dictionary views --

     def viewkeys(self):
         "od.viewkeys() -> a set-like object providing a view on od's keys"
         return KeysView(self)

     def viewvalues(self):
         "od.viewvalues() -> an object providing a view on od's values"
         return ValuesView(self)

     def viewitems(self):
         "od.viewitems() -> a set-like object providing a view on od's items"
         return ItemsView(self)

OrderdDict Code

我们都知道字典本来是无序的，它依靠key，value之间的索引进行匹配，那么有序字典的原理是什么呢? 原理： dic = {'k2':1,'k1':2}，li = ['k1','k2']，这个字典在内部维护了一个key列表。

从上面的图中我们就知道，尽管我们定义的字典是从1到8按顺序写的，但是在打印的过程当中并没有按到我们希望的顺序打印。这个时候有序字典的优势就出来了：

3、默认字典(defaultdict)

defaultdict是对字典的类型的补充，他默认给字典的值设置了一个类型。

 class defaultdict(dict):
     """
     defaultdict(default_factory[, ...]) --> dict with default factory

     The default factory is called without arguments to produce
     a new value when a key is not present, in __getitem__ only.
     A defaultdict compares equal to a dict with the same items.
     All remaining arguments are treated the same as if they were
     passed to the dict constructor, including keyword arguments.
     """
     def copy(self): # real signature unknown; restored from __doc__
         """ D.copy() -> a shallow copy of D. """
         pass

     def __copy__(self, *args, **kwargs): # real signature unknown
         """ D.copy() -> a shallow copy of D. """
         pass

     def __getattribute__(self, name): # real signature unknown; restored from __doc__
         """ x.__getattribute__('name') <==> x.name """
         pass

     def __init__(self, default_factory=None, **kwargs): # known case of _collections.defaultdict.__init__
         """
         defaultdict(default_factory[, ...]) --> dict with default factory

         The default factory is called without arguments to produce
         a new value when a key is not present, in __getitem__ only.
         A defaultdict compares equal to a dict with the same items.
         All remaining arguments are treated the same as if they were
         passed to the dict constructor, including keyword arguments.

         # (copied from class doc)
         """
         pass

     def __missing__(self, key): # real signature unknown; restored from __doc__
         """
         __missing__(key) # Called by __getitem__ for missing key; pseudo-code:
           if self.default_factory is None: raise KeyError((key,))
           self[key] = value = self.default_factory()
           return value
         """
         pass

     def __reduce__(self, *args, **kwargs): # real signature unknown
         """ Return state information for pickling. """
         pass

     def __repr__(self): # real signature unknown; restored from __doc__
         """ x.__repr__() <==> repr(x) """
         pass

     default_factory = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
     """Factory for default value called by __missing__()."""

 defaultdict

defaultdict Code

用代码实现了下述功能

有如下值集合 [11,22,33,44,55,66,77,88,99,90...]，将所有大于 66 的值保存至字典的第一个key中，将小于 66 的值保存至第二个key的值中。

即： {'k1': 大于66 , 'k2': 小于66}

看出神奇的地方了么？我们可以不需要在空字典中指定value的值，直接执行append，就可以向字典中插入值了，就是因为我们使用defauldict(list)方式定义了一个value值默认为list的字典。

否则我们就要这么写才行：

 lst = [11,22,33,44,55,66,77,88,99,90]
 dic = {}
 for l in lst:
     if l >= 66:
         if 'k2'in dic.keys():
             dic['k2'].append(l)
         else:
             dic['k2'] = [l,]
     else:
         if 'k1'in dic.keys():
             dic['k1'].append(l)
         else:
             dic['k1'] = [l,]
 print dic

普通字典的实现方式

4、可命名元组(namedtuple)

根据nametuple可以创建一个包含tuple所有功能以及其他功能的类型。

 class Mytuple(__builtin__.tuple)
  |  Mytuple(x, y)
  |
  |  Method resolution order:
  |      Mytuple
  |      __builtin__.tuple
  |      __builtin__.object
  |
  |  Methods defined here:
  |
  |  __getnewargs__(self)
  |      Return self as a plain tuple.  Used by copy and pickle.
  |
  |  __getstate__(self)
  |      Exclude the OrderedDict from pickling
  |
  |  __repr__(self)
  |      Return a nicely formatted representation string
  |
  |  _asdict(self)
  |      Return a new OrderedDict which maps field names to their values
  |
  |  _replace(_self, **kwds)
  |      Return a new Mytuple object replacing specified fields with new values
  |
  |  ----------------------------------------------------------------------
  |  Class methods defined here:
  |
  |  _make(cls, iterable, new=<built-in method __new__ of type object>, len=<built-in function len>) from __builtin__.type
  |      Make a new Mytuple object from a sequence or iterable
  |
  |  ----------------------------------------------------------------------
  |  Static methods defined here:
  |
  |  __new__(_cls, x, y)
  |      Create new instance of Mytuple(x, y)
  |
  |  ----------------------------------------------------------------------
  |  Data descriptors defined here:
  |
  |  __dict__
  |      Return a new OrderedDict which maps field names to their values
  |
  |  x
  |      Alias for field number 0
  |
  |  y
  |      Alias for field number 1
  |
  |  ----------------------------------------------------------------------
  |  Data and other attributes defined here:
  |
  |  _fields = ('x', 'y')
  |
  |  ----------------------------------------------------------------------
  |  Methods inherited from __builtin__.tuple:
  |
  |  __add__(...)
  |      x.__add__(y) <==> x+y
  |
  |  __contains__(...)
  |      x.__contains__(y) <==> y in x
  |
  |  __eq__(...)
  |      x.__eq__(y) <==> x==y
  |
  |  __ge__(...)
  |      x.__ge__(y) <==> x>=y
  |
  |  __getattribute__(...)
  |      x.__getattribute__('name') <==> x.name
  |
  |  __getitem__(...)
  |      x.__getitem__(y) <==> x[y]
  |
  |  __getslice__(...)
  |      x.__getslice__(i, j) <==> x[i:j]
  |
  |      Use of negative indices is not supported.
  |
  |  __gt__(...)
  |      x.__gt__(y) <==> x>y
  |
  |  __hash__(...)
  |      x.__hash__() <==> hash(x)
  |
  |  __iter__(...)
  |      x.__iter__() <==> iter(x)
  |
  |  __le__(...)
  |      x.__le__(y) <==> x<=y
  |
  |  __len__(...)
  |      x.__len__() <==> len(x)
  |
  |  __lt__(...)
  |      x.__lt__(y) <==> x<y
  |
  |  __mul__(...)
  |      x.__mul__(n) <==> x*n
  |
  |  __ne__(...)
  |      x.__ne__(y) <==> x!=y
  |
  |  __rmul__(...)
  |      x.__rmul__(n) <==> n*x
  |
  |  __sizeof__(...)
  |      T.__sizeof__() -- size of T in memory, in bytes
  |
  |  count(...)
  |      T.count(value) -> integer -- return number of occurrences of value
  |
  |  index(...)
  |      T.index(value, [start, [stop]]) -> integer -- return first index of value.
  |      Raises ValueError if the value is not present.

 Mytuple

 Mytuple

namedtuple Code

主要用于‘坐标’的表示。用法如下：

5、双向队列(deque)

一个线程安全的双向队列：双向队列我们可以理解为两个栈底相连的栈，和队列的先进先出不同，元素可以从这个队列的两端分别加入或者删除值。尽管list其实完全可以实现这个功能，但是python的collections类还是很贴心的把这些方法都归纳了出来，歪果仁就是有意思啊~~~

 class deque(object):
     """
     deque([iterable[, maxlen]]) --> deque object

     Build an ordered collection with optimized access from its endpoints.
     """
     def append(self, *args, **kwargs): # real signature unknown
         """ Add an element to the right side of the deque. """
         pass

     def appendleft(self, *args, **kwargs): # real signature unknown
         """ Add an element to the left side of the deque. """
         pass

     def clear(self, *args, **kwargs): # real signature unknown
         """ Remove all elements from the deque. """
         pass

     def count(self, value): # real signature unknown; restored from __doc__
         """ D.count(value) -> integer -- return number of occurrences of value """
         return 0

     def extend(self, *args, **kwargs): # real signature unknown
         """ Extend the right side of the deque with elements from the iterable """
         pass

     def extendleft(self, *args, **kwargs): # real signature unknown
         """ Extend the left side of the deque with elements from the iterable """
         pass

     def pop(self, *args, **kwargs): # real signature unknown
         """ Remove and return the rightmost element. """
         pass

     def popleft(self, *args, **kwargs): # real signature unknown
         """ Remove and return the leftmost element. """
         pass

     def remove(self, value): # real signature unknown; restored from __doc__
         """ D.remove(value) -- remove first occurrence of value. """
         pass

     def reverse(self): # real signature unknown; restored from __doc__
         """ D.reverse() -- reverse *IN PLACE* """
         pass

     def rotate(self, *args, **kwargs): # real signature unknown
         """ Rotate the deque n steps to the right (default n=1).  If n is negative, rotates left. """
         pass

     def __copy__(self, *args, **kwargs): # real signature unknown
         """ Return a shallow copy of a deque. """
         pass

     def __delitem__(self, y): # real signature unknown; restored from __doc__
         """ x.__delitem__(y) <==> del x[y] """
         pass

     def __eq__(self, y): # real signature unknown; restored from __doc__
         """ x.__eq__(y) <==> x==y """
         pass

     def __getattribute__(self, name): # real signature unknown; restored from __doc__
         """ x.__getattribute__('name') <==> x.name """
         pass

     def __getitem__(self, y): # real signature unknown; restored from __doc__
         """ x.__getitem__(y) <==> x[y] """
         pass

     def __ge__(self, y): # real signature unknown; restored from __doc__
         """ x.__ge__(y) <==> x>=y """
         pass

     def __gt__(self, y): # real signature unknown; restored from __doc__
         """ x.__gt__(y) <==> x>y """
         pass

     def __iadd__(self, y): # real signature unknown; restored from __doc__
         """ x.__iadd__(y) <==> x+=y """
         pass

     def __init__(self, iterable=(), maxlen=None): # known case of _collections.deque.__init__
         """
         deque([iterable[, maxlen]]) --> deque object

         Build an ordered collection with optimized access from its endpoints.
         # (copied from class doc)
         """
         pass

     def __iter__(self): # real signature unknown; restored from __doc__
         """ x.__iter__() <==> iter(x) """
         pass

     def __len__(self): # real signature unknown; restored from __doc__
         """ x.__len__() <==> len(x) """
         pass

     def __le__(self, y): # real signature unknown; restored from __doc__
         """ x.__le__(y) <==> x<=y """
         pass

     def __lt__(self, y): # real signature unknown; restored from __doc__
         """ x.__lt__(y) <==> x<y """
         pass

     @staticmethod # known case of __new__
     def __new__(S, *more): # real signature unknown; restored from __doc__
         """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
         pass

     def __ne__(self, y): # real signature unknown; restored from __doc__
         """ x.__ne__(y) <==> x!=y """
         pass

     def __reduce__(self, *args, **kwargs): # real signature unknown
         """ Return state information for pickling. """
         pass

     def __repr__(self): # real signature unknown; restored from __doc__
         """ x.__repr__() <==> repr(x) """
         pass

     def __reversed__(self): # real signature unknown; restored from __doc__
         """ D.__reversed__() -- return a reverse iterator over the deque """
         pass

     def __setitem__(self, i, y): # real signature unknown; restored from __doc__
         """ x.__setitem__(i, y) <==> x[i]=y """
         pass

     def __sizeof__(self): # real signature unknown; restored from __doc__
         """ D.__sizeof__() -- size of D in memory, in bytes """
         pass

     maxlen = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
     """maximum size of a deque or None if unbounded"""

     __hash__ = None

 deque

deque Code