理解venv module in Python

• venv

  documents

  source code

  《理解site，site-packages in Python》

  PEP 405

  Creating a virtual environment

  PEP405 proposes adding a new venv module to the standard library which implements the creation of virtual environments.

  The venv module provides support for creating lightweight “virtual environments” with their own site directories, optionally isolated from system site directories.

  Each virtual environment has its own Python binary (which matches the version of the binary that was used to create this environment) and can have its own independent set of installed Python packages in its site directories.

• Virtual environment layout

  A typical virtual environment layout on a POSIX system would be:

  pyvenv.cfg
  bin/python3
  bin/python
  bin/pysetup3
  include/
  lib/python3.3/site-packages/
  

  While on a Windows system:

  pyvenv.cfg
  Scripts/python.exe
  Scripts/python3.dll
  Scripts/pysetup3.exe
  Scripts/pysetup3-script.py
  		... other DLLs and pyds...
  Include/
  Lib/site-package
  

  Third-party packages installed into the virtual environment will have their Python modules placed in the site-packages directory, and their executables placed in bin/ or Scripts.

• Splitting the meanings of sys.prefix

  sys.prefix is describes as “A string giving the site-specific directory prefix where the platform independent Python files are installed.” Bu default, this is the string '/usr/local'.

  If a virtual environment is in effect, this value will be changed in site.py to point to the virtual environment. The value for the Python installation will still be avaiable, via base_prefix.

  The standard library and header files as found under sys.prefix, but without site-packages.

• 安装及使用

  python标准库

  不同于作为application的virtualenv, venv更多是作为module library存在,当然也可以通过python -m venv来调用scripts.

  python -m venv pro
  source pro/bin/activate # 激活
  deactivate
  rm -rf pro
  

• References

1. [Lib/venv/ : Creation of virtual environments](Lib/venv/ : Creation of virtual environments )