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
1、创建一个有序字典
import collections dic = collections.OrderedDict() dic['k1'] = 'v1' dic['k2'] = 'v2' dic['k3'] = 'v3'
2、查看有序字典
print(dic) 输出结果： OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')])
3、对比有序字典和字典
import collections dic1 = collections.OrderedDict() # 有序字典 dic1['k1'] = 'v1' dic1['k2'] = 'v2' dic1['k3'] = 'v3' dic2 = dict() # 字典 dic2['k1'] = 'v1' dic2['k2'] = 'v2' dic2['k3'] = 'v3' print(dic) 输出结果 OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')]) # 有序的 {'k2': 'v2', 'k1': 'v1', 'k3': 'v3'} #无序的
4、查看有序字典的方法
>>> dir(dic) ['_OrderedDict__hardroot', '_OrderedDict__map', '_OrderedDict__marker', '_OrderedDict__root', '_OrderedDict__update', '__class__', '__contains__', '__delattr__', '__delitem__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'clear', 'copy', 'fromkeys', 'get', 'items', 'keys', 'move_to_end', 'pop', 'popitem', 'setdefault', 'update', 'values']
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)
5、有序字典的常用操作方法
# setdefault 设置新键的值，默认为None import collections dic = collections.OrderedDict() dic['k1'] = 'v1' dic['k2'] = 'v2' dic['k3'] = 'v3' dic['k4'] = None dic.setdefault('k5') dic.setdefault('k6', 'v6') print(dic)
输出结果： OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3'), ('k4', None), ('k5', None), ('k6', 'v6')])
# move_to_end 移动某个key到最后 import collections dic = collections.OrderedDict() dic['k1'] = 'v1' dic['k2'] = 'v2' dic['k3'] = 'v3' print(dic) dic.move_to_end('k1') print(dic) 输出结果： OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')]) OrderedDict([('k2', 'v2'), ('k3', 'v3'), ('k1', 'v1')])
# pop 删除某个key import collections dic = collections.OrderedDict() dic['k1'] = 'v1' dic['k2'] = 'v2' dic['k3'] = 'v3' print(dic) dic.pop('k2') ret = dic.pop('k2') print(dic) print(ret) 输出结果： OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')]) OrderedDict([('k1', 'v1'), ('k3', 'v3')]) v2
# update 新增某个key或刷新某个key值 import collections dic = collections.OrderedDict() dic['k1'] = 'v1' dic['k2'] = 'v2' dic['k3'] = 'v3' print(dic) dic.update({'k1':'v111','k10':'v10'}) print(dic) 输出结果： OrderedDict([('k1', 'v1'), ('k2', 'v2'), ('k3', 'v3')]) OrderedDict([('k1', 'v111'), ('k2', 'v2'), ('k3', 'v3'), ('k10', 'v10')])