无法在ubuntu上运行python3

Question

I can't run python3 on ubuntu 14.04

alias python=python3
python --version

outputs:

Python 2.7.6

and

python3 --version

gives same output

As I understand python3 should be preinstalled on the system?

I tried to run:

sudo apt-get install python3

But there is an error:

  Setting up idle-python3.4 (3.4.3-1ubuntu1~14.04.3) ...
  File "/usr/lib/python3.4/compileall.py", line 120
    print('*** ', end='')
                     ^
SyntaxError: invalid syntax
dpkg: error processing package idle-python3.4 (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 idle-python3.4

Answer 1

Check if python3 is installed:

python3 --version

Add alias python=python3 into ~/.bashrc or ~/.bash_aliases file.

You must logout then login again.

I recommend using python3 for python 3.x. There are a lot of programs depending on python 2.x so better not to remove it. However you can uninstall it: sudo apt-get remove python2.7

Before uninstalling Python 2.7 read this .

Answer 2

You misunderstand how aliases work. You need to reset the hash table via hash -r (see man bash for details).

Also:

edd@max:~$ python3 --version
Python 3.5.1+
edd@max:~$ lsb_release -d
Description:    Ubuntu 16.04 LTS
edd@max:~$ 

and

edd@max:~$ ls -l /usr/bin/python*
lrwxrwxrwx 1 root root       9 Dec  9  2015 /usr/bin/python -> python2.7
lrwxrwxrwx 1 root root       9 Dec  9  2015 /usr/bin/python2 -> python2.7
-rwxr-xr-x 1 root root 2629712 Aug 11  2011 /usr/bin/python2.6
-rwxr-xr-x 1 root root 3546104 Jul  2 14:05 /usr/bin/python2.7
lrwxrwxrwx 1 root root      33 Jul  2 14:05 /usr/bin/python2.7-config -> x86_64-linux-gnu-python2.7-config
lrwxrwxrwx 1 root root      16 Dec  9  2015 /usr/bin/python2-config -> python2.7-config
lrwxrwxrwx 1 root root       9 Mar 23 06:00 /usr/bin/python3 -> python3.5
lrwxrwxrwx 1 root root      11 Oct 19  2012 /usr/bin/python3.2 -> python3.2mu
-rwxr-xr-x 1 root root 2863832 Oct 19  2012 /usr/bin/python3.2mu
-rwxr-xr-x 2 root root 4439120 Mar 31 06:51 /usr/bin/python3.5
-rwxr-xr-x 2 root root 4439120 Mar 31 06:51 /usr/bin/python3.5m
lrwxrwxrwx 1 root root      10 Mar 23 06:00 /usr/bin/python3m -> python3.5m
lrwxrwxrwx 1 root root      16 Dec  9  2015 /usr/bin/python-config -> python2.7-config
lrwxrwxrwx 1 root root      58 Mar 25 17:01 /usr/bin/pythontex -> ../share/texlive/texmf-dist/scripts/pythontex/pythontex.py
-rwxr-xr-x 1 root root     306 Mar 25 17:01 /usr/bin/pythontex3
edd@max:~$ 

You want to look into dpkg-alternatives to switch the default from python2 to python3 . I'd be careful though as some system scripts may expect python to be version 2.