在Windows 10下的Ubuntu安裝Python+pyenv

因為想寫一些Python程序，所以今天在家中的Windows 10安裝Python。也因為習慣及相容性考慮，目前首選使用Linux，再利用pyenv 做Version管理及Python虛疑環境。

安裝Ubuntu (on Windows 10)

除了Windows 10自帶的Linux子系統WSL（也是Ubuntu)，Canonical Group Limited也在MS Store 發佈了Ubuntu。目前我是選擇MS Store 的Ubuntu。只要到MS Store找出Ubuntu並安裝即可。詳細安裝可參考 WSL-Windows 10 Installation Guide

在Linux子系統上安裝Python

安裝好Linux子系統後，就算不帶Python的，也可直接安裝pyenv再安裝Python [不確定，待驗証]，但我發現某些情況也要在系統上安裝同版本的Python。其中例子是npyscreen所依賴的curses/ncurses，因為WSL下的Python3並未帶curses，所以就算成功安裝npyscreen可會報錯，不能使用。經多次試驗發現如想在pyenv下的Python能正常使用curses/ncurses就必需在Linux子系統上也安裝Python+ncurses。

安裝pyenv

以住用VirtualEnv來做Python Version管理，但用過pyenv之後就愛上她。Ubuntu 本自帶Python3，但在pyenv環境也可另行安裝Python3。

首先，打開「Windows上Ubuntu的Bash」，輸入以下指令安裝pyenv所需的軟件套裝:

# Required libraries
$ sudo apt-get install git gcc make openssl libssl-dev libbz2-dev libreadline-dev libsqlite3-dev zlib1g-dev

# For convenience, install the development tools
$ sudo apt-get install build-essential

利用pyenv-installer安裝pyenv及pyenv-virtualenv：

$ curl -L https://github.com/pyenv/pyenv-installer/raw/master/bin/pyenv-installer | bash
$ pyenv update

修改 ~/.bashrc ，把以下的pyenv所需的指令加到最後：

# Update ~/.bashrc and add pyenv required commands:
$ vi ~/.bashrc

export PATH="~/.pyenv/bin:$PATH"
eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"

# Restart shell
$ exec $SHELL

安裝Python:

# Show available versions:
$ pyenv install --list

# Install 3.6.7
$ pyenv install 3.6.7

（注意，當前Python3 最新版為3.7.1，但經pyenv安裝時報錯，所以轉用3.6.7)

Downloading Python-3.7.1.tar.xz...
-> https://www.python.org/ftp/python/3.7.1/Python-3.7.1.tar.xz
Installing Python-3.7.1...

BUILD FAILED (Ubuntu 18.04 using python-build 1.2.8)

Inspect or clean up the working tree at /tmp/python-build.20181030235256.31820
Results logged to /tmp/python-build.20181030235256.31820.log

Last 10 log lines:
  File "/tmp/tmpgw81w9h4/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/__init__.py", line 42, in <module>
  File "/tmp/tmpgw81w9h4/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/cmdoptions.py", line 16, in <module>
  File "/tmp/tmpgw81w9h4/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/index.py", line 25, in <module>
  File "/tmp/tmpgw81w9h4/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/download.py", line 39, in <module>
  File "/tmp/tmpgw81w9h4/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/utils/glibc.py", line 3, in <module>
  File "/tmp/python-build.20181030235256.31820/Python-3.7.1/Lib/ctypes/__init__.py", line 7, in <module>
    from _ctypes import Union, Structure, Array
ModuleNotFoundError: No module named '_ctypes'
Makefile:1122: recipe for target 'install' failed
make: *** [install] Error 1

Create first virtualenv for practice

$ pyenv virtualenv 3.6.7 my-exec-001

# Show current installed versions
$ pyenv versions
  3.6.7
  3.6.7/envs/my-exec-001
  my-exec-001

# Enter to the shell:
$ pyenv shell my-exec-001

# Also update the pip
$ pip install --upgrade pip