python如何建立venv虚拟环境

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。

官方文档参考

https://docs.python.org/3/library/venv.html