问题
Currently when I use "python" command, it points to python2.6. I have installed python3.1 and I want the "python" command point to python3.1. How it is possible?
mahmood@mpc:~$ which python
/usr/bin/python
mahmood@mpc:~$ ls -l /usr/bin/python
lrwxrwxrwx 1 root root 9 2010-11-24 16:14 /usr/bin/python -> python2.6
mahmood@mpc:~$ uname -a
Linux orca 2.6.32-24-server #39-Ubuntu SMP Wed Jul 28 06:21:40 UTC 2010 x86_64 GNU/Linux
回答1:
Since you have Linux, and if you want to simply type "python" instead of "python3" in order to run Python programs, a solution is simply to define an alias in you shell configuration file (.bashrc, etc.). For Bourne shells, it should be something like
alias python=python3
(or whatever your Python 3 name is).
This way, you do not have to change anything on your system, so this solution should quite innocuous and it should not break your system.
回答2:
You really don't want to change what python points to, because some programs might expect Python 2, and break.
The solution is to use virtualenv: create an isolated Python 3 environment (with the -p python3 option), activate it, and you're good to go.
回答3:
It is not advisable.
You could write at the top in your own script (a shebang):
#!/usr/bin/env python3
If you're on Windows then install pylauncher. It understands #!.
On Linux to make your script executable, run once:
$ chmod +x your-script
After that, to run your script:
$ ./your-script
For interactive use you could create virtualenv as @Petr Viktorin points out. To install/upgrade (versions from Ubuntu's repositries are too old):
$ pip install -U virtualenv{,wrapper}
Follow instructions in /path/to/virtualenvwrapper.sh, to create virtualenv that uses python3:
$ mkvirtualenv --python python3 py3
To activate virtualenv:
$ workon py3
In an active virtualenv python refers to /path/virtualenv/bin/python. So you could run:
$ python your_module.py
回答4:
You could follow this procedure:
sudo rm /usr/bin/python
sudo ln -s /usr/bin/python3.1 /usr/bin/python
But as already stated by Petr Viktorin, any programs that would expect python v2 would stop to work. So use with caution. You can undo the change by running:
sudo rm /usr/bin/python
sudo ln -s /usr/bin/python2.6 /usr/bin/python
回答5:
unlink /usr/bin/python
ln -s /usr/bin/python3.1 /usr/bin/python
回答6:
On Linux/Mac OS you can use python3 instead of python.
回答7:
Try update-alternatives for Linux.
来源：https://stackoverflow.com/questions/7679674/changing-default-python-to-another-version