创建虚拟环境
在当前目录创建虚拟环境：
$ python -m venv .1
下面是”venv”的详细使用参数:
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)
激活虚拟环境
在Posix标准平台下：
$ source <venv>/bin/activate
在Windows cmd下：
C:> <venv>/Scripts/activate.bat
在Windows PowerShell下：
PS C:> <venv>/Scripts/Activate.ps1
测试虚拟环境
激活虚拟环境后，在命令行会提示当前虚拟环境的名称，就表示激活成功了。
在当前虚拟环境中安装numpy:
$ pip install numpy
当前安装的numpy包与系统中的不会冲突，下面进行测试：
$ python >>> import numpy >>> print(numpy)
如果输出了numpy的包路径就表示一切正常。
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