在阿里云服务器上，用virtualenv创建虚拟环境时，报了个错误

root@iZwz982qla1uxm1s5dnyo7Z:/usr/lib/python3/dist-packages/virtualenv-15.0.1.egg-info# virtualenv -p python3 venv
Running virtualenv with interpreter /usr/bin/python2
New python executable in /usr/lib/python3/dist-packages/virtualenv-15.0.1.egg-info/venv/bin/python2
Not overwriting existing python script /usr/lib/python3/dist-packages/virtualenv-15.0.1.egg-info/venv/bin/python (you must use /usr/lib/python3/dist-packages/virtualenv-15.0.1.egg-info/venv/bin/python2)
Please make sure you remove any previous custom paths from your /root/.pydistutils.cfg file.
 1 [global]
Installing setuptools, pkg_resources, pip, wheel...
 Complete output from command /usr/lib/python3/dis...nfo/venv/bin/python2 - setuptools pkg_resources pip wheel:
 Collecting setuptools
 Downloading http://mirrors.aliyun.com/pypi/packages/ff/f4/385715ccc461885f3cedf57a41ae3c12b5fec3f35cce4c8706b1a112a133/setuptools-40.0.0-py2.py3-none-any.whl (567kB)
Collecting pkg_resources
Exception:
Traceback (most recent call last):
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/basecommand.py", line 209, in main
 status = self.run(options, args)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/commands/install.py", line 328, in run
 wb.build(autobuilding=True)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/wheel.py", line 748, in build
 self.requirement_set.prepare_files(self.finder)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/req/req_set.py", line 360, in prepare_files
 ignore_dependencies=self.ignore_dependencies))
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/req/req_set.py", line 512, in _prepare_file
 finder, self.upgrade, require_hashes)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/req/req_install.py", line 273, in populate_link
 self.link = finder.find_requirement(self, upgrade)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/index.py", line 442, in find_requirement
 all_candidates = self.find_all_candidates(req.name)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/index.py", line 400, in find_all_candidates
 for page in self._get_pages(url_locations, project_name):
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/index.py", line 545, in _get_pages
 page = self._get_page(location)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/index.py", line 648, in _get_page
 return HTMLPage.get_page(link, session=self.session)
 File "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl/pip/index.py", line 760, in get_page
 resp.raise_for_status()
 File "/usr/lib/python3/dist-packages/virtualenv-15.0.1.egg-info/venv/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/models.py", line 840, in raise_for_status
 raise HTTPError(http_error_msg, response=self)
HTTPError: 404 Client Error: Not Found for url: http://mirrors.aliyun.com/pypi/simple/pkg-resources/
----------------------------------------
...Installing setuptools, pkg_resources, pip, wheel...done.
Traceback (most recent call last):
 File "/usr/lib/python3/dist-packages/virtualenv.py", line 2363, in <module>
 main()
 File "/usr/lib/python3/dist-packages/virtualenv.py", line 719, in main
 symlink=options.symlink)
 File "/usr/lib/python3/dist-packages/virtualenv.py", line 988, in create_environment
 download=download,
 File "/usr/lib/python3/dist-packages/virtualenv.py", line 918, in install_wheel
 call_subprocess(cmd, show_stdout=False, extra_env=env, stdin=SCRIPT)
 File "/usr/lib/python3/dist-packages/virtualenv.py", line 812, in call_subprocess
 % (cmd_desc, proc.returncode))
OSError: Command /usr/lib/python3/dis...nfo/venv/bin/python2 - setuptools pkg_resources pip wheel failed with error code 2

看到HTTPError: 404 Client Error: Not Found for url: http://mirrors.aliyun.com/pypi/simple/pkg-resources/以为是阿里云的安全组配置没配好，折腾了半天，原来是访问PyPI镜像源出了问题，将pip的默认的源地址改为国内源即可。

具体操作如下：

vim ~/.pip/pip.conf打开pip配置文件:

写入

[global]
index-url = http://e.pypi.python.org/simple

以下这几个国内源都可以

e.pypi.python.org

pypi.douban.com

pypi.hustunique.com

补充：使用virtualenv创建Python3.7虚拟环境时报错ModuleNotFoundError: No module named '_ctypes'的解决方法

使用virtualenv创建Python3.7.6版本虚拟环境时，遇到了标题中的报错，记录一下解决过程。

出现这种情况一般是因为缺少依赖包libffi-devel

在安装3.7以上版本时，需要一个新的libffi-devel包做依赖

使用yum安装依赖

yum install libffi-devel -y

删除之前安装的报错的虚拟环境目录

rm -f venv

重新编译安装系统Python3.7.6（需要先找到安装时的Python源码包，cd到目录中）

./configure --prefix=/usr/local/python3
make && make install

删除之前建立的软连接

rm -rf /usr/bin/python3
rm -rf /usr/bin/pip3

重新建立软连接

ln -s /usr/local/python3/bin/python3.7 /usr/bin/python3
ln -s /usr/local/python3/bin/pip3.7 /usr/bin/pip3

到此Python3重新安装完成，可以用python3、pip3命令测试一下是否安装成功。

进入虚拟目录将要存放的目录，使用新安装的Python3创建虚拟环境。此处需要使用-p参数指定Python版本路径，否则默认创建Python2的环境。

virtualenv -p /usr/bin/python3 venv

测试进入创建好的虚拟环境中

source venv/bin/activate

退出环境

deactivate

以上为个人经验，希望能给大家一个参考，也希望大家多多支持python博客。如有错误或未考虑完全的地方，望不吝赐教。