Unable to determine SOCKS version from socks://127.0.0.1:1080/
File “/home/dlnu/.virtualenvs/python2.7/local/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/contrib/socks.py”, line 154, in init
“Unable to determine SOCKS version from %s” % proxy_url
ValueError: Unable to determine SOCKS version from socks://127.0.0.1:1080/
（1）使用命令：sudo pip install numpy时，可能遇到：
The directory ‘/Users/huangqizhi/Library/Caches/pip’ or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo’s -H flag.
BST树算法掌握不够熟练 对递归有了更深的了解
找最大，最小节点，插入节点，查找节点，遍历不算太难 注意细心
删除某个节点有三种可能（考虑root节点是否为空）
1.删除叶子节点
2.删除只有左子树或者只有右子树的节点（要考虑它是否为根节点，考虑它是父节点的左孩子还是右孩子）
3.删除既有左子树也有右子树的节点（找大于它的最小值—->找右子树中最左边的节点，替换该节点位置的值，并删除这个最左边的节点（要考虑这个节点是否有右子树，是父节点的左孩子还是右孩子))
通过SSH访问服务器，难免会要用到压缩，解压缩，打包，解包等，这时候tar命令就是是必不可少的一个功能强大的工具。linux中最流行的tar是麻雀虽小，五脏俱全，功能强大。
Implement a MapSum class with insert, and sum methods.
For the method insert, you’ll be given a pair of (string, integer). The string represents the key and the integer represents the value. If the key already existed, then the original key-value pair will be overridden to the new one.