Ubuntuにpip3がデフォで入ってない

インストール手順

Ubuntu バージョン確認

grep -n "" /etc/*release
/etc/lsb-release:1:DISTRIB_ID=Ubuntu
/etc/lsb-release:2:DISTRIB_RELEASE=18.04
/etc/lsb-release:3:DISTRIB_CODENAME=bionic
/etc/lsb-release:4:DISTRIB_DESCRIPTION="Ubuntu 18.04 LTS"
/etc/os-release:1:NAME="Ubuntu"
/etc/os-release:2:VERSION="18.04 LTS (Bionic Beaver)"
/etc/os-release:3:ID=ubuntu
/etc/os-release:4:ID_LIKE=debian
/etc/os-release:5:PRETTY_NAME="Ubuntu 18.04 LTS"
/etc/os-release:6:VERSION_ID="18.04"
/etc/os-release:7:HOME_URL="https://www.ubuntu.com/"
/etc/os-release:8:SUPPORT_URL="https://help.ubuntu.com/"
/etc/os-release:9:BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
/etc/os-release:10:PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
/etc/os-release:11:VERSION_CODENAME=bionic
/etc/os-release:12:UBUNTU_CODENAME=bionic

pipがあるか確認

sudo apt-cache search pip | grep -E 'python[0-9]*-pip'
python-pip - Python package installer
python-pip-whl - Python package installer
python3-pip - Python package installer

python3-pipがpip3らしいのでインストール

sudo apt-get install python3-pip
pip3 --version
pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6)

シンボリックリンクも登録しておく

まずpythonのシンボリックリンクを確認

ls -al /usr/bin/python*
lrwxrwxrwx 1 root root       9  4月 16  2018 /usr/bin/python -> python2.7*
lrwxrwxrwx 1 root root       9  4月 16  2018 /usr/bin/python2 -> python2.7*
-rwxr-xr-x 1 root root 3633560  4月 16  2018 /usr/bin/python2.7*
lrwxrwxrwx 1 root root       9  6月 22 06:52 /usr/bin/python3 -> python3.6*
lrwxrwxrwx 1 root root      16  6月 22 06:52 /usr/bin/python3-config -> python3.6-config*
-rwxr-xr-x 1 root root    1018 10月 29  2017 /usr/bin/python3-jsondiff*
-rwxr-xr-x 1 root root    3661 10月 29  2017 /usr/bin/python3-jsonpatch*
-rwxr-xr-x 1 root root    1342  5月  2  2016 /usr/bin/python3-jsonpointer*
-rwxr-xr-x 1 root root     398 11月 16  2017 /usr/bin/python3-jsonschema*
-rwxr-xr-x 2 root root 4567672  9月 13 03:26 /usr/bin/python3.6*
lrwxrwxrwx 1 root root      33  9月 13 03:26 /usr/bin/python3.6-config -> x86_64-linux-gnu-python3.6-config*
-rwxr-xr-x 2 root root 4567672  9月 13 03:26 /usr/bin/python3.6m*
lrwxrwxrwx 1 root root      34  9月 13 03:26 /usr/bin/python3.6m-config -> x86_64-linux-gnu-python3.6m-config*
lrwxrwxrwx 1 root root      10  6月 22 06:52 /usr/bin/python3m -> python3.6m*
lrwxrwxrwx 1 root root      17  6月 22 06:52 /usr/bin/python3m-config -> python3.6m-config*

pip3のシンボリックリンクも合わせる感じで登録しておく。
(pipが入ってなく、特に呼び分けたりする必要もないので、今回はやめ)

ls -al /usr/bin/pip*
-rwxr-xr-x 1 root root 293  5月 17 01:28 /usr/bin/pip3*