看例子：
>>> ctree
BinaryTree({9: 'scree'})
>>> ctree.clear() #清空数据
>>> ctree
BinaryTree({})
>>> ctree.is_empty()
True
>>> btree
BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
>>> btree.is_empty()
False
- 根据key、value循环从树中取值：
>>.items([reverse])--按照(key,value)结构取值;
>>.keys([reverse])--key
>>.values([reverse])--value. O(n)
>>.iter_items(s,e[,reverse]--s,e是key的范围，也就是生成在某个范围内的key的迭代器 O(n)
看例子：
>>> btree
BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
>>> for (k,v) in btree.items():
... print k,v
...
2 phone
7 computer
9 scree
github qiwsir
>>> for k in btree.keys():
... print k
...
2
7
9
github
>>> for v in btree.values():
... print v
...
phone
computer
scree
qiwsir
>>> for (k,v) in btree.items(reverse=True): #反序
... print k,v
...
github qiwsir
9 scree
7 computer
2 phone
>>> btree
BinaryTree({2: 'phone', 5: None, 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
>>> for (k,v) in btree.iter_items(6,9): #要求迭代6<=key<9的键值对数据
... print k,v
...
7 computer
8 eight
>>>
- 删除数据并返回该值：
>>.pop(key[,d]), 根据key删除树的数据，并返回该value，但是如果没有，并也指定了备选返回的d，则返回d，如果没有d，则报错；
>>.pop_item(),在树中随机选择(key,value)删除，并返回。
看例子：
>>> ctree = btree.copy()
>>> ctree
BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
>>> ctree.pop(2) #删除key=2的数据，返回其value
'phone'
>>> ctree.pop(2) #删除一个不存在的key，报错
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python2.7/site-packages/bintrees/abctree.py", line 350, in pop
value = self.get_value(key)
File "/usr/local/lib/python2.7/site-packages/bintrees/abctree.py", line 557, in get_value
raise KeyError(str(key))
KeyError: '2'
>>> ctree.pop_item() #随机返回一个(key,value),并已删除之
(7, 'computer')
>>> ctree
BinaryTree({9: 'scree', 'github': 'qiwsir'})
>>> ctree.pop(7,"sing") #如果没有，可以返回指定值
'sing'
- 查找数据,并返回value： .set_default(key[,d])，在树的数据中查找key,如果存在，则返回该value。如果不存在，当指定了d,则将该（key,d）添加到树内；当不指定d的时候，添加(key,None). O(log(n))
看例子：
>>> btree
BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
>>> btree.set_default(7) #存在则返回
'computer'
>>> btree.set_default(8,"eight") #不存在，则返回后备指定值，并加入到树
'eight'
>>> btree
BinaryTree({2: 'phone', 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
>>> btree.set_default(5) #如果不指定值，则会加入None
>>> btree
BinaryTree({2: 'phone', 5: None, 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
>>> btree.get(2) #注意，.get(key)与.set_default(key[,d])的区别
'phone'
>>> btree.get(3,"mobile") #不存在的 key,返回但不增加到树
'mobile'
>>> btree
BinaryTree({2: 'phone', 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
