pyenv 是一套管理同時使用不同版本 Python 的工具，也可以搭配 virtualenv 使用。
首先依照 Common build problems 安裝一些套件，由於等一下也會使用到 git 所以一併安裝。
$ sudo apt-get install -y make build-essential libssl-dev zlib1g-dev libbz2-dev libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev git
然後執行官方建議的安裝方式。
$ wget https://raw.githubusercontent.com/yyuu/pyenv-installer/master/bin/pyenv-installer -O - | bash
然後我不是很喜歡每次啟動 shell 就會自動載入使用 pyenv，所以我自己寫了一個 ~/bin/pyenv 的腳本程式來使用。
#!/bin/bash
export PATH="$HOME/.pyenv/bin:$PATH"
eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"
export PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h(python)\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
bash --noprofile -l
每次當我要使用 pyenv 時，就要先執行一次 pyenv，接下來我就可以看到 (python) 的提示出現，代表我正在使用 pyenv。
fourdollars@ubuntu(python):~$
接下來來找找看，有哪些 Python 版本可以安裝使用。
$ pyenv install -l
Available versions:
...
2.7.10
...
3.4.3
...
我選擇安裝最新(寫這篇文章時)的 Python 2 的穩定發行版本。
$ pyenv install 2.7.10
Downloading Python-2.7.10.tgz...
-> https://yyuu.github.io/pythons/eda8ce6eec03e74991abb5384170e7c65fcd7522e409b8e83d7e6372add0f12a
Installing Python-2.7.10...
patching file ./Lib/site.py
Installed Python-2.7.10 to /home/fourdollars/.pyenv/versions/2.7.10
然後先切進 2.7.10 的環境，更新一下套件。
$ pyenv global 2.7.10
$ pip list --outdated | awk '{print $1}' | xargs pip install --upgrade
You are using pip version 6.1.1, however version 7.1.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
You are using pip version 6.1.1, however version 7.1.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
Collecting setuptools
Downloading setuptools-18.3.1-py2.py3-none-any.whl (462kB)
100% |████████████████████████████████| 462kB 666kB/s
Collecting pip
Using cached pip-7.1.2-py2.py3-none-any.whl
Installing collected packages: setuptools, pip
Found existing installation: setuptools 15.2
Uninstalling setuptools-15.2:
Successfully uninstalled setuptools-15.2
Found existing installation: pip 6.1.1
Uninstalling pip-6.1.1:
Successfully uninstalled pip-6.1.1
Successfully installed pip-7.1.2 setuptools-18.3.1
接下來要搭配使用 virtualenv 建立一個獨立的 Python 環境。
$ pyenv virtualenv 2.7.10 watchdog
Collecting virtualenv
Downloading virtualenv-13.1.2-py2.py3-none-any.whl (1.7MB)
100% |████████████████████████████████| 1.7MB 345kB/s
Installing collected packages: virtualenv
Successfully installed virtualenv-13.1.2
New python executable in /home/fourdollars/.pyenv/versions/watchdog/bin/python2.7
Also creating executable in /home/fourdollars/.pyenv/versions/watchdog/bin/python
Installing setuptools, pip, wheel...done.
Ignoring indexes: https://pypi.python.org/simple
Requirement already satisfied (use --upgrade to upgrade): setuptools in /home/fourdollars/.pyenv/versions/watchdog/lib/python2.7/site-packages
Requirement already satisfied (use --upgrade to upgrade): pip in /home/fourdollars/.pyenv/versions/watchdog/lib/python2.7/site-packages
接下來要建立一個 watchdog 專案目錄，並且在裡面設定使用這個獨立的 Python 環境。
$ mkdir ~/watchdog && cd ~/watchdog
$ pyenv local watchdog
$ pyenv local
watchdog
也就是說在這個目錄底下，pyenv 會自動切進跟專案目錄名稱相同的 virtualenv 環境。
接下來總算可以安裝 Django 來開發了。
$ pip install Django
Collecting Django
Downloading Django-1.8.4-py2.py3-none-any.whl (6.2MB)
100% |████████████████████████████████| 6.2MB 110kB/s
Installing collected packages: Django
Successfully installed Django-1.8.4
安裝完 Django 後要重新登入一下，才可以使用 django-admin 的指令來建立這個新專案。
fourdollars@ubuntu(python):~/watchdog$ django-admin startproject watchdog .
然後就是 Django 的初始化跟啟動開發用的伺服器。
$ python manage.py migrate
Operations to perform:
Synchronize unmigrated apps: staticfiles, messages
Apply all migrations: admin, contenttypes, auth, sessions
Synchronizing apps without migrations:
Creating tables...
Running deferred SQL...
Installing custom SQL...
Running migrations:
Rendering model states... DONE
Applying contenttypes.0001_initial... OK
Applying auth.0001_initial... OK
Applying admin.0001_initial... OK
Applying contenttypes.0002_remove_content_type_name... OK
Applying auth.0002_alter_permission_name_max_length... OK
Applying auth.0003_alter_user_email_max_length... OK
Applying auth.0004_alter_user_username_opts... OK
Applying auth.0005_alter_user_last_login_null... OK
Applying auth.0006_require_contenttypes_0002... OK
Applying sessions.0001_initial... OK
fourdollars@ubuntu(python):~/watchdog$ python manage.py runserver
Performing system checks...
System check identified no issues (0 silenced).
September 08, 2015 - 09:50:59
Django version 1.8.4, using settings 'watchdog.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
