python如何建立venv虚拟环境[python高级教程]

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)

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

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。

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

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