title: "which python" keeps showing python2 path after changing the alias of "python" to python3
body: <p>I'm a Mac user. When I typed <code>python</code> in the terminal, it launched python2 located at <code>/usr/bin/python</code> But I wish to use python3. So I added <code>alias python='/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7'</code> and
  <code>alias python2='/usr/bin/python'</code> in the <code>~/.bash_profile</code></p>
  
  <p>Then when I typed <code>python</code> again, it launched python3 as my wish, and I can still use python2 when typing <code>python2</code> in the terminal. However, if I type <code>which python</code>, the terminal still showed me <code>/usr/bin/python</code> (the old python2 path) plus there's no output if I type <code>which python2</code>.</p>
  
  <p>I am not familiar with bash. I am not sure if this has anything to do with environment variables. I tried to search. But still couldn't solve this inconsistency. Can anyone please let me know how I can obtain the correct python3 path when typing <code>which python</code>? Thanks!</p>