PEP405 规范流程图

PEP405 提出为Python增加一个自带site directories的轻量级虚拟环境(virtual environments)机制。列出PEP405英文部分摘要

This PEP proposes to add to Python a mechanism for lightweight “virtual environments” with their own site directories, optionally isolated from system site directories. Each virtual environment has its own Python binary (allowing creation of environments with various Python versions) and can have its own independent set of installed Python packages in its site directories, but shares the standard library with the base installed Python.

该提案围绕寻找

sys.prefix

的值展开，新添了一步以寻找

pyvenv.cfg

文件判断

sys.prefix

值的操作规范。下面就绘制出流程图:

Created with Raphaël 2.1.0prefix 相关值未确定pyvenv.cfg文件是否被找到home=h-value 格式是否被找到sys.prefix = path/to/directory of pyvenv.cfg sys.base_prefix = h-valueprefix 相关值确定sys.prefix与sys.base_prefix等值yesnoyesno

site

模块和

sysconfig

模块通过

sys.base_prefix

/

sys.base_exec_prefix

来确定Python标准库和头文件位置，通过

sys.prefix

/

sys.exec_prefix

来确定

site-packages

目录的位置。