On 01/24/2015 05:27 AM, 杨令 wrote:

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From: Chi Hsuan Yen To: General Discussion about Arch Linux Cc: Date: Fri, 23 Jan 2015 21:51:00 +0800 Subject: [arch-general] An archlinux-python package for managing system default python version? Dear Arch enthusiasts,

The package extra/java-runtime-common provides a convenient script archlinux-java to handle co-existing JDK/JRE versions. I can use it to switch between different versions of java implementations to accomplish numerous tasks from testing the compatibilities of my programs to running third party applications targeting on different platforms. Now I hope there's also a simple script for the same thing but for python. On the system, most of the scripts are written for python2 and some other scripts are python3-specific. In most cases it's not a problem because I can fix the scripts or use some tricks like $PATH to ensure the correct execution of the programs. However, in large projects, doing either is time-consuming and costly. Recently I'm building CyanogenMod on Arch Linux. It includes lots of python scripts in the build system, and most of them requires python2. Using the tip provided on the article about Python on ArchWiki prevents lots of problems, but, however, some scripts have the shebang line "#!/usr/bin/env python" or are invoked by some command like "/usr/bin/python ...". I have to change the link /usr/bin/python to pointing to python2 for further progress on building and changed it back for my daily use. If there's an archlinux-python script, lots of time on battling the difference between python2 and python3 does not exist anymore, which I believe lots of users can benefit from it. Any ideas?

sudo pacman -S python-virtualenv python2-virtualenv python-virtualenvwrapper

Google how to use them.

Actually virtualenv itself is enough. virtualenvwrapper is a useful wrapper, so I recommend to use them together.

Here is my virtualenv and virtualenvwrapper configuration in .zshrc. You can take a look:

# Python virtualenvwrapper export WORKON_HOME=$HOME/.virtualenvs #export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python2

if [ -f /usr/bin/virtualenvwrapper.sh ]; then source /usr/bin/virtualenvwrapper.sh fi

# Python pip -> virtualenv only export PIP_REQUIRE_VIRTUALENV=true export PIP_RESPECT_VIRTUALENV=true

Correct me if I'm wrong, but virtualenv can support only the python versions that virtualenv is build on. For example in arch repos there are the latest 2 and 3 python versions. In ruby, rvm/rbenv you can install **any** ruby version and use that per project or globally, etc. Now, in python there is pyenv[0] which is as the author states, a fork of rbenv ported to python. [0] https://github.com/yyuu/pyenv -- GPG : 0x3A7DDABC985EDC6E Blog: http://axilleas.me