Ubuntu 20.04 に Python 2.7 をインストール（OS標準？）

# はじめに

Ubuntu 20.04にPython 2.7をインストール

> In 20.04 LTS, the python included in the base system is Python 3.8. Python 2.7 has been moved to universe and is not included by default in any new installs.
>
> Remaining packages in Ubuntu which require Python 2.7 have been updated to use /usr/bin/python2 as their interpreter, and /usr/bin/python is not present by default on any new installs. On systems upgraded from previous releases, /usr/bin/python will continue to point to python2 for compatibility. Users who require /usr/bin/python for compatibility on newly-installed systems are encouraged to install the python-is-python3 package, for a /usr/bin/python pointing to python3 instead.

> 引用元 : [FocalFossa/ReleaseNotes \- Ubuntu Wiki](https://wiki.ubuntu.com/FocalFossa/ReleaseNotes#Python3_by_default)

## サポート

保守期間不明。
OS EOLまで保守されるのだろうか？

## LOG その1

### インストール

```shell-session
# cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

# apt update; apt install -y python
... 略
```

### 各種確認

```shell-session
# which python{,2,3}
/usr/bin/python
/usr/bin/python2

# ll /usr/bin/python*
lrwxrwxrwx. 1 root root       7 Apr 15 10:45 /usr/bin/python -> python2*
lrwxrwxrwx. 1 root root       9 Mar 13 12:31 /usr/bin/python2 -> python2.7*
-rwxr-xr-x. 1 root root 3694632 Apr  7 12:05 /usr/bin/python2.7*

# python -V
Python 2.7.18rc1

# apt show python
Package: python
State: not a real package (virtual)
N: Can't select candidate version from package python as it has no candidate
N: Can't select versions from package 'python' as it is purely virtual
N: No packages found

# apt show python2
Package: python2
Version: 2.7.17-2ubuntu4
Priority: optional
Section: universe/python
Source: python-defaults
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: Matthias Klose <doko@debian.org>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 139 kB
Provides: python-ctypes, python-email, python-importlib, python-profiler, python-wsgiref
Pre-Depends: python2-minimal (= 2.7.17-2ubuntu4)
Depends: python2.7 (>= 2.7.17~rc1-1~), libpython2-stdlib (= 2.7.17-2ubuntu4)
Suggests: python2-doc (= 2.7.17-2ubuntu4), python-tk (>= 2.7.17~rc1-1~)
Conflicts: python-central (<< 0.5.5)
Breaks: python (<< 2.7.15-2), update-manager-core (<< 0.200.5-2)
Replaces: python (<< 2.7.15-2), python-dev (<< 2.6.5-2)
Homepage: https://www.python.org/
Task: ubuntustudio-desktop-core, ubuntustudio-desktop
Download-Size: 26.5 kB
APT-Manual-Installed: no
APT-Sources: http://archive.ubuntu.com/ubuntu focal/universe amd64 Packages
Description: interactive high-level object-oriented language (Python2 version)
```

## LOG その2

### インストール

```shell-session
# cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

# apt update; apt install -y python2
... 略
```

### 各種確認

```shell-session
# which python{,2,3}
/usr/bin/python2

# ll /usr/bin/python*
lrwxrwxrwx. 1 root root       9 Mar 13 12:31 /usr/bin/python2 -> python2.7*
-rwxr-xr-x. 1 root root 3694632 Apr  7 12:05 /usr/bin/python2.7*

# python2 -V
Python 2.7.18rc1

# apt show python2
Package: python2
Version: 2.7.17-2ubuntu4
Priority: optional
Section: universe/python
Source: python-defaults
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: Matthias Klose <doko@debian.org>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 139 kB
Provides: python-ctypes, python-email, python-importlib, python-profiler, python-wsgiref
Pre-Depends: python2-minimal (= 2.7.17-2ubuntu4)
Depends: python2.7 (>= 2.7.17~rc1-1~), libpython2-stdlib (= 2.7.17-2ubuntu4)
Suggests: python2-doc (= 2.7.17-2ubuntu4), python-tk (>= 2.7.17~rc1-1~)
Conflicts: python-central (<< 0.5.5)
Breaks: python (<< 2.7.15-2), update-manager-core (<< 0.200.5-2)
Replaces: python (<< 2.7.15-2), python-dev (<< 2.6.5-2)
Homepage: https://www.python.org/
Task: ubuntustudio-desktop-core, ubuntustudio-desktop
Download-Size: 26.5 kB
APT-Manual-Installed: yes
APT-Sources: http://archive.ubuntu.com/ubuntu focal/universe amd64 Packages
Description: interactive high-level object-oriented language (Python2 version)
```