尝试运行Python 3.4.3但仍然显示Python 2.7.9

I installed Python 3.4.3 and then installed Python 2.7.9 on Mac Air. If I run Python on a command line, it shows Python 2.7.9. I removed Python 2.7.9, it still shows Python 2.7.9. What is the problem? Thanks.I installed Python 3.4.3 and then installed Pyt