python下pip安装总是报 AssertionError

PS C:\WINDOWS\system32> pip install sys
Collecting sys
Using cached sys-0.9.tar.gz
Complete output from command python setup.py egg_info:
Traceback (most recent call last):
File "", line 1, in
File "c:\users\ynf19\appdata\local\temp\pip-build-9qorpr\sys\setup.py", line 1, in
raise AssertionError("This package must not be installed from pypi")
AssertionError: This package must not be installed from pypi

这是因为sys是标准库内置的类库，它不能通过pypi来安装，你可以直接import

http://blog.csdn.net/julyraining/article/details/51834964