title: How to add a new Pydev Interpreter in Eclipse
body: <p>Ok so I have Pydev installed on 2 machines.  For some reason I have 3.5.1 on a laptop and 2.7 on the desktop.  Now a project I have on the 2.7 machine (desktop) throws syntax errors on the other machine (laptop), which I guess must be because they are running different versions of Python, since I can't see any other possible cause.  As such, I installed 2.7 on the laptop, but before attempting to change the default interpreter to 2.7 (which I may or may not have done correctly: I just added the 2.7 path and moved it to the top of the list of (2) interpreters) I tried fiddling with the launch preferences in an effort to make it work.  Now when I try running the project, I get this: </p>
  
  <p><a href="https://imgur.com/0n63S0t" rel="nofollow noreferrer">https://imgur.com/0n63S0t</a></p>
  
  <p>I tried googling things like 'how to add new interpreter in PyDev' but didn't find anything which helped.  Anyone know what on earth is going and how I might get the project which works fine on the desktop working on the laptop as well?</p>
  
  <p>I've noticed in this question:</p>
  
  <p><a href="https://stackoverflow.com/questions/46165453/setting-default-python-grammar-version-in-eclipse-pydev">Setting default Python grammar version in Eclipse PyDev</a></p>
  
  <p>that it basically asks what may be the same thing (although I'm not sure the result I get which I showed in the imgur link is actually to do with the Python version so this problem may not be the same as that in the other question I linked: it seems I may have 2 problems: 1 which is similar to that in the question I linked and a new 1 (shown in the imgur link, at the bottom, where it says 'Ran 0 tests in 0.000 s) possibly caused by fiddling with the launch preferences).  My question is how to proceed on the laptop so that I can make the project work.  Could I do this by removing Python 3.5.1?  Is it not possible to have 2 different versions of Python on the same machine and to choose which you use for each given project?  If it is possible, how do you do this?  I actually tried removing 3.5.1 from the interpreters but the result is the same and when I checked the interpreters again, 3.5.1 was still there, so I would also like to know how to remove an interpreter.  Everything about this seems so incredibly awkward.  Genuinely have no idea why things should be make so awkard.</p>
  
  <p>Edit: I think I've successfully changed the interpreter that's being used, thanks to Joe, but I still get the useless result when I run that I posted in the imgur link.  It looks like it's running a 'Python unit-test' (whatever that is) and I want to restore it to what it used to do, which was just a standard run. Any ideas appreciated.</p>
  
  <p>Edit 2: turns out it just runs as whatever you last ran it as, by default and no option to change this, it seems.</p>