本文翻译自：Using Python 3 in virtualenv
Using virtualenv , I run my projects with the default version of Python (2.7). 使用virtualenv ，我使用默认版本的Python（2.7）运行项目。 On one project, I need to use Python 3.4. 在一个项目中，我需要使用Python 3.4。
I used brew install python3 to install it on my Mac. 我使用brew install python3将其安装在Mac上。 Now, how do I create a virtualenv that uses the new version? 现在，如何创建使用新版本的virtualenv？
eg sudo virtualenv envPython3 例如sudo virtualenv envPython3
If I try: 如果我尝试：
virtualenv -p python3 test
I get: 我得到：
Running virtualenv with interpreter /usr/local/bin/python3
Using base prefix '/usr/local/Cellar/python3/3.4.0_1/Frameworks/Python.framework/Versions/3.4'
New python executable in test/bin/python3.4
Also creating executable in test/bin/python
Failed to import the site module
Traceback (most recent call last):
File "/Users/user/Documents/workspace/test/test/bin/../lib/python3.4/site.py", line 67, in <module>
import os
File "/Users/user/Documents/workspace/test/test/bin/../lib/python3.4/os.py", line 634, in <module>
from _collections_abc import MutableMapping
ImportError: No module named '_collections_abc'
ERROR: The executable test/bin/python3.4 is not functioning
ERROR: It thinks sys.prefix is '/Users/user/Documents/workspace/test' (should be '/Users/user/Documents/workspace/test/test')
ERROR: virtualenv is not compatible with this system or executable
#1楼
参考：https://stackoom.com/question/1c2Zt/在virtualenv中使用Python
#2楼
simply run 只需运行
virtualenv -p python3 envname
Update after OP's edit: OP编辑后更新：
There was a bug in the OP's version of virtualenv, as described here . 有没有在OP的版本virtualenv中的一个bug，如所描述这里 。 The problem was fixed by running: 该问题已通过运行解决：
pip install --upgrade virtualenv
#3楼
Python 3 has a built-in support for virtual environments - venv . Python 3具有对虚拟环境venv的内置支持。 It might be better to use that instead. 最好改用它。 Referring to the docs: 参考文档：
Creation of virtual environments is done by executing the pyvenv script: 通过执行pyvenv脚本来创建虚拟环境：
pyvenv /path/to/new/virtual/environment
Update for Python 3.6 and newer: 适用于Python 3.6及更高版本的更新：
As pawciobiel correctly comments , pyvenv is deprecated as of Python 3.6 and the new way is: 当pawciobiel正确注释时 ，从Python 3.6开始不推荐使用 pyvenv ，新方法是：
python3 -m venv /path/to/new/virtual/environment
#4楼
In addition to the other answers, I recommend checking what instance of virtualenv you are executing: 除了其他答案，我建议检查您正在执行哪个virtualenv实例：
which virtualenv
If this turns up something in /usr/local/bin, then it is possible - even likely - that you installed virtualenv (possibly using an instance of easy_tools or pip) without using your system's package manager (brew in OP's case). 如果在/ usr / local / bin中出现问题，则可能甚至可能安装了virtualenv（可能使用easy_tools或pip实例）而没有使用系统的程序包管理器（在OP中为棕色）。 This was my problem. 这是我的问题。
Years ago - when I was even more ignorant - I had installed virtualenv and it was masking my system's package-provided virtualenv. 多年前-当我更加无知的时候-我安装了virtualenv，它掩盖了我系统的软件包提供的virtualenv。
After removing this old, broken virtualenv, my problems went away. 删除了这个破旧的virtualenv之后，我的问题就消失了。
#5楼
I'v tried pyenv and it's very handy for switching python versions (global, local in folder or in the virtualenv): 我尝试过pyenv ，它对于切换python版本（全局，文件夹或virtualenv中的本地）非常方便：
brew install pyenv
then install Python version you want: 然后安装所需的Python版本：
pyenv install 3.5.0
and simply create virtualenv with path to needed interpreter version: 并只需创建virtualenv并包含所需解释器版本的路径即可：
virtualenv -p /Users/johnny/.pyenv/versions/3.5.0/bin/python3.5 myenv
That's it, check the version: 就是这样，检查版本：
. ./myenv/bin/activate && python -V
There are also plugin for pyenv pyenv-virtualenv but it didn't work for me somehow. 也有pyenv的插件pyenv-virtualenv，但是它对我不起作用。
#6楼
对我有用
virtualenv --no-site-packages --distribute -p /usr/bin/python3 ~/.virtualenvs/py3
