Python3.3以上的版本通过venv模块原生支持虚拟环境，可以代替之前的virtualenv。
该venv模块提供了创建轻量级“虚拟环境”，提供与系统Python的隔离支持。每一个虚拟环境都有其自己的Python二进制（允许有不同的Python版本创作环境），并且可以拥有自己独立的一套Python包。
注意：python3.3中使用”venv”命令创建的环境不包含”pip”，需进行手动安装。Python3.4中改进了这一缺陷。
创建虚拟环境
python -m venv myvenv
此命令会在当前目录下生成一个名为myvenv的目录，myenv也是创建的虚拟环境名。
激活环境：
/Scripts/activate.bat
退出环境：
/Scripts/deactivate.bat
附：
venv使用参数：
usage: venv [-h] [--system-site-packages] [--symlinks] [--clear]
[--upgrade] [--without-pip] ENV_DIR [ENV_DIR ...] Creates virtual Python environments in one or more target directories. positional arguments:
ENV_DIR A directory to create the environment in. optional arguments:
-h, --help show this help message and exit
--system-site-packages Give access to the global site-packages dir to the
virtual environment.
--symlinks Try to use symlinks rather than copies, when symlinks
are not the default for the platform.
--copies Try to use copies rather than symlinks, even when
symlinks are the default for the platform.
--clear Delete the environment directory if it already exists.
If not specified and the directory exists, an error is
raised.
--upgrade Upgrade the environment directory to use this version
of Python, assuming Python has been upgraded in-place.
--without-pip Skips installing or upgrading pip in the virtual
environment (pip is bootstrapped by default)