1.输入 sudo add-apt-repository ppa:jonathonf/python-3.6
ubuntu@VM-0-13-ubuntu:~$ sudo add-apt-repository ppa:jonathonf/python-3.6
A plain backport of *just* Python 3.6. System extensions/Python libraries may or may not work.
Don't remove Python 3.5 from your system - it will break.
More info: https://launchpad.net/~jonathonf/+archive/ubuntu/python-3.6
Press [ENTER] to continue or ctrl-c to cancel adding it
gpg: keyring `/tmp/tmpo9itxaur/secring.gpg' created
gpg: keyring `/tmp/tmpo9itxaur/pubring.gpg' created
gpg: requesting key F06FC659 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpo9itxaur/trustdb.gpg: trustdb created
gpg: key F06FC659: public key "Launchpad PPA for J Fernyhough" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
OK提示 ok后就没问题，如果显示超时就请再一次输入刚刚那个命令。
2.输入 sudo apt-get update
就会出现如图代码显示在更新中。
ubuntu@VM-0-13-ubuntu:~$ sudo apt-get update
Hit:1 http://mirrors.tencentyun.com/ubuntu xenial InRelease
Hit:2 http://mirrors.tencentyun.com/ubuntu xenial-security InRelease
Hit:3 http://mirrors.tencentyun.com/ubuntu xenial-updates InRelease
Get:4 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial InRelease [18.0 kB]
Get:5 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial/main amd64 Packages [4,760 B]
Get:6 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial/main i386 Packages [4,748 B]
94% [Waiting for headers] update命令，会访问源列表里的每个网址，并读取软件列表，然后保存在本地电脑。我们在新立得软件包管理器里看到的软件列表，都是通过update命令更新的。
upgrade命令，会把本地已安装的软件，与刚下载的软件列表里对应软件进行对比，如果发现已安装的软件版本太低，就会提示你更新。
输入命令 sudo apt-get install python3.6
安装python3.6
ubuntu@VM-0-13-ubuntu:~$ sudo apt-get install python3.6
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
libpython3.6-minimal libpython3.6-stdlib python3.6-minimal
Suggested packages:
python3.6-venv python3.6-doc binfmt-support
The following NEW packages will be installed:
libpython3.6-minimal libpython3.6-stdlib python3.6 python3.6-minimal
0 upgraded, 4 newly installed, 0 to remove and 198 not upgraded.
Need to get 4,505 kB of archives.
After this operation, 23.1 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial/main amd64 libpython3.6-minimal amd64 3.6.5-5~16.04.york1 [574 kB]
Get:2 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial/main amd64 python3.6-minimal amd64 3.6.5-5~16.04.york1 [1,712 kB]
Get:3 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial/main amd64 libpython3.6-stdlib amd64 3.6.5-5~16.04.york1 [1,989 kB]
Get:4 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu xenial/main amd64 python3.6 amd64 3.6.5-5~16.04.york1 [230 kB]
Fetched 4,505 kB in 13s (330 kB/s)
Selecting previously unselected package libpython3.6-minimal:amd64.
(Reading database ... 66624 files and directories currently installed.)
Preparing to unpack .../libpython3.6-minimal_3.6.5-5~16.04.york1_amd64.deb ...
Unpacking libpython3.6-minimal:amd64 (3.6.5-5~16.04.york1) ...
Selecting previously unselected package python3.6-minimal.
Preparing to unpack .../python3.6-minimal_3.6.5-5~16.04.york1_amd64.deb ...
Unpacking python3.6-minimal (3.6.5-5~16.04.york1) ...
Selecting previously unselected package libpython3.6-stdlib:amd64.
Preparing to unpack .../libpython3.6-stdlib_3.6.5-5~16.04.york1_amd64.deb ...
Unpacking libpython3.6-stdlib:amd64 (3.6.5-5~16.04.york1) ...
Selecting previously unselected package python3.6.
Preparing to unpack .../python3.6_3.6.5-5~16.04.york1_amd64.deb ...
Unpacking python3.6 (3.6.5-5~16.04.york1) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for mime-support (3.59ubuntu1) ...
Setting up libpython3.6-minimal:amd64 (3.6.5-5~16.04.york1) ...
Setting up python3.6-minimal (3.6.5-5~16.04.york1) ...
Setting up libpython3.6-stdlib:amd64 (3.6.5-5~16.04.york1) ...
Setting up python3.6 (3.6.5-5~16.04.york1) ...
ubuntu@VM-0-13-ubuntu:~$ 这样就显示python3.6安装成功了。
但是还需要设置一下python3之间的优先级和py2和py3的优先级。
输入 python 你会发现py2还是默认的python
ubuntu@VM-0-13-ubuntu:~$ python
Python 2.7.12 (default, Dec 4 2017, 14:50:18)
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
ubuntu@VM-0-13-ubuntu:~$ 现在应该更改默认值，python默认为Python2，现在修改为Python3
ubuntu@VM-0-13-ubuntu:~$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 100
update-alternatives: using /usr/bin/python2 to provide /usr/bin/python (python) in auto mode
ubuntu@VM-0-13-ubuntu:~$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 150
update-alternatives: using /usr/bin/python3 to provide /usr/bin/python (python) in auto mode现在查看一下python
ubuntu@VM-0-13-ubuntu:~$ python
Python 3.5.2 (default, Nov 23 2017, 16:37:01)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 发现python3.5 优先于python3.6
现在我们需要更改python3.5为3.6
ubuntu@VM-0-13-ubuntu:~$ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.5 1
update-alternatives: using /usr/bin/python3.5 to provide /usr/bin/python3 (python3) in auto mode
ubuntu@VM-0-13-ubuntu:~$ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.6 2
update-alternatives: using /usr/bin/python3.6 to provide /usr/bin/python3 (python3) in auto mode现在查看一下修改成功了没有。
ubuntu@VM-0-13-ubuntu:~$ python
Python 3.6.5 (default, May 3 2018, 10:08:28)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 你会发现python3.6是默认的python版本了。
补充问题
安装python3.6后，发现安装pip出现了一些问题。
输入命令sudo apt-get install python-pip安装pip这个问题
因为现在安装的是python3.6所以应该是sudo apt-get install python3-pip