Uploading your experiment to Pack&Go

Here are a few things you should keep in mind when preparing your MATLAB experiment for Pack&Go:

• If your experiment contains subfolders, remember to replace any local file paths in your code with relative paths. Do not hardcode your file paths. For more details, see Best Practices for Designing and Implementing Pack&Go Studies

• Pack&Go does not support the MATLAB addpath function.

• The MATLAB command window will not be visible, or accessible, in online experiments; avoid using functions like ‘input()’ which prompts users to enter input in the command window.

• Save all result files in the main experiment folder. Do not create result subfolders.

• Pack&Go runs on a remote server with an optimized Linux X64 operating system. If you are using third-party MEX files in your experiment, make sure you specifically include Linux X64 MEX files.

Here are a few things you should keep in mind when preparing your Python/PsychoPy experiment for Pack&Go:

• If your experiment contains subfolders, remember to replace any local file paths in your code with relative paths. Do not hardcode your file paths. For more details, see Best Practices for Designing and Implementing Pack&Go Studies

• If you are using keyboard input in your study, use the Keyboard class from PsychoPy, not the event class. E.g.
  Bad:

  Python

  from psychopy import event
  
  # Wait for spacebar press to start
  event.waitKeys(keyList=['space'])
  

  Good:

  from psychopy.hardware import keyboard   
  kb = keyboard.Keyboard()
  
  # Wait for spacebar press to exit
  kb.waitKeys(keyList=['space'])
  

• If you are playing audio in your PsychoPy experiment, you must initialize the audio by including the following lines at the start of your code:

  Python

  from psychopy import prefs
  prefs.hardware['audioLib'] = ['pygame']
  from psychopy import sound
  

• Our service uses the X Window System and therefore you will need to add the following at the beginning of the experiment script for optimal timing:

  Python

  import ctypes
  xlib = ctypes.cdll.LoadLibrary("libX11.so")
  xlib.XInitThreads()
  

• If your experiment uses any libraries besides Python’s standard library and PsychoPy (e.g. numpy and matplotlib), you must also include in the zipped folder, a requirements text file (named “requirements.txt”) which specifies which packages will need to be included on the server to run your experiment. This file should be in the root of the zipped folder, not a subfolder. For example, the following in a text file will tell us to include the version of ‘matplotlib’ 3.7.3 and ‘numpy’ 1.24.4:

  matplotlib==3.7.3
  numpy==1.24.4
  

• For a general explanation about the requirements.txt file and how to create it see this resource: https://learnpython.com/blog/python-requirements-file/

• If you’re not sure which versions exist for a module, you can search for it here: https://pypi.org/

• Python IDE users can try the following to automatically generate their requirements.txt:

  Python

  pip freeze > requirements.txt
  

  This will generate a list of ALL dependencies currently installed. We recommend reviewing this .txt and eliminating any packages not used in your experiment, in order to optimize performance.