title: Running python programmes for the command line
body: <p>I am trying to run a python programme called helloWorld.py from the command line on MacOS.</p>
  
  <p>I am typing into bash:</p>
  
  <pre><code>Ryans-MacBook-Air:~ ryanunderwood$ python3 helloWorld.py
  </code></pre>
  
  <p>But I am getting the following:</p>
  
  <pre><code>/Library/Frameworks/Python.framework/Versions/3.7/Resources/Python.app/Contents/MacOS/Python: can't open file 'helloWorld.py': [Errno 2] No such file or directory
  </code></pre>
  
  <p>There is definitely a file with this name in the directory. Why is this programme not running?</p>