为什么我不能使用 python 虽然它告诉我 python3 已经是最新版本 (3.5.1-3)

Question

I want to use python in my ubuntu. When I use python command it tell me:

dc2-user@10-254-6-144:~$ python
The program 'python' can be found in the following packages:
* python-minimal
* python3
Ask your administrator to install one of them

then I try to install it:

dc2-user@10-254-6-144:~$ sudo apt-get install python3
Reading package lists... Done
Building dependency tree       
Reading state information... Done
python3 is already the newest version (3.5.1-3).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

but as you can see, it seemed that I have already installed python3.5 Then I uninstall it and install it,through

sudo apt-get remove python3.5
sudo apt-get install python3.5

but still cant use python command.
Generally, I can use python command after install it.I dont know what happend and where I should do next?

Answer 1

Ubuntu does only install Python 3 and won't add a link from /usr/bin/python3 to /usr/bin/python

So you are forced to:

• Use python3

or

• Add a link yourself or an alias or another shell based solution

Reference:

• https://wiki.ubuntu.com/Python/3

Quoting:

• Python 3 will be the only Python version installed by default.
• Python 3 will be the only Python version in any installation media (ie image ISOs)
• Only Python 3 will be allowed on the Ubuntu touch images.
• All upstream libraries that support Python 3 will have their Python 3 version available in the archive.
• All applications that run under Python 3 will use Python 3 by default.
• All system scripts in the archive will use Python 3.

and

• /usr/bin/python will point to Python 3. No, this is not going to happen (unless PEP 394 advocates otherwise, which is doubtful for the foreseeable future). /usr/bin/python and /usr/bin/python2 will point to Python 2.7 and /usr/bin/python3 will point to the latest supported Python 3 version.

Answer 2

Try using update-alternatives

I ended up with this issue after trying update-alternatives and incorrectly changing symblinks

Viewing sudo update-alternatives --config python shows you what the system is using.

You can override that with something like the below:

sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.8 20

Resolve - Too many levels of symbolic links

If you get Error too many levels of symbolic links Then make sure to double check the symbolic links in /etc/alternatives/

cd /etc/alternatives
find . -maxdepth 1 -type l -ls | grep python

The culprit, in the search results you'll see something like this

./python -> /usr/bin/python3

That's a python symlink pointing to python3.

If you go into /usr/bin you'll probably find that:

./python3 -> /etc/alternatives/python

You have 2 symlinks pointing to each other and hence you get the 'Too many symbolic links' error

What you have to do in this case is delete one of them and recreate it. In my case I deleted /etc/alternatives/python symlink and repointed it to python 3.8

cd /etc/alternatives/
sudo rm -r ./python
sudo ln -s /usr/bin/python3.8 ./python

Now typing python, brings up the standard 3.8 welcome, in place of that error in the op

Python 3.8.0 (default, Oct 14 2019, 23:13:30)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

Answer 3

您是否尝试过运行sudo python3因为您似乎已经安装了 python

Answer 4

安装 python-minimal 使用命令sudo apt install python-minimal python-minimal 解决了我的问题，我也设法在我的流浪服务器上解决了它。