Changing symlink "python" to "python3" causes problems

Changing symlink "python" to "python3" causes problems

I have Python 2.7.3 and 3.2.3 installed on my Ubuntu 12.04 64bit (by
default?). When I type "python", I want python 3.2 instead of 2.7.
Changing symlink "python" to link to python3 seems to cause big problems.
Why is that and is there a way to do that?
lrwxrwxrwx 1 root root 7 Sep 28 19:15 python -> python2
lrwxrwxrwx 1 root root 9 Jun 18 13:26 python2 -> python2.7
-rwxr-xr-x 1 root root 2993592 Apr 10 02:46 python2.7
-rwxr-xr-x 1 root root 1652 Apr 10 02:46 python2.7-config
lrwxrwxrwx 1 root root 16 Jun 18 13:26 python2-config ->
python2.7-config
lrwxrwxrwx 1 root root 9 Apr 10 17:12 python3 -> python3.2
lrwxrwxrwx 1 root root 11 Apr 10 02:13 python3.2 -> python3.2mu
-rwxr-xr-x 1 root root 2949952 Apr 10 02:13 python3.2mu
lrwxrwxrwx 1 root root 11 Apr 10 17:12 python3mu -> python3.2mu
lrwxrwxrwx 1 root root 16 Jun 18 13:26 python-config -> python2.7-config
I linked python to python3:
sudo ln -fs python3 python
It worked but later it forced me to change the link back because Ubuntu
seems not much responsive and I can't run most of the applications any
more, such as Variety, Spyder, Okular, Software Center, etc.