使用pip安裝一個python庫時提示pip版本過低，需要升級，執行 pip install--upgrade pip 後提示：

Collecting pip

  Using cached pip-8.1.0-py2.py3-none-any.whl

Installing collected packages: pip

  Found existing installation: pip 8.0.2

    Uninstalling pip-8.0.2:

Exception:

Traceback (most recent call last):

  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/basecommand.py", line 209, in main

    status = self.run(options, args)

  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/commands/install.py", line 317, in run

    prefix=options.prefix_path,

  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/req/req_set.py", line 725, in install

    requirement.uninstall(auto_confirm=True)

  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/req/req_install.py", line 752, in uninstall

    paths_to_remove.remove(auto_confirm)

  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/req/req_uninstall.py", line 115, in remove

    renames(path, new_path)

  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/utils/__init__.py", line 266, in renames

    shutil.move(old, new)

  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 300, in move

    rmtree(src)

  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 247, in rmtree

    rmtree(fullname, ignore_errors, onerror)

  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 252, in rmtree

    onerror(os.remove, fullname, sys.exc_info())

  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 250, in rmtree

    os.remove(fullname)

OSError: [Errno 13] Permission denied: '/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/EGG-INFO/dependency_links.txt'

好像是許可權問題，網上一頓搜尋，各種英文答案看不太明白，突然在一個頁面看到：sudo 這個詞 ，試了一下：

sudo  pip install --upgrade pip

ok了！！！！！

特此紀念。