Printing to the Console (stdout) from a Pulse Sequence

When debugging a pulse sequence's code (sequence and binning), it's useful to be able to see the output of print statements. This document tells you how to enable that.

Where Not to Look

In the lower left of the pulse sequence editor's test tab there's [attachment:screenshot.png a "console" window] that starts with the message "Welcome to the Pulse Sequence Editor". The output of Python print statements will not appear there. That console only displays specific messages from the pulse sequence editor.

So Where is stdout?

When you run Simulation from a desktop shortcut, it executes Python in a shell that's either hidden or disappears as soon as the application exits. (The behavior depends on which operating system you run.) A slight alteration of the command in the desktop shortcut will allow you to see the command shell.

Specific instructions for Windows, OS X and Linux are below.

Windows XP

  1. Right click on the Simulation desktop shortcut. Windows will display a popup menu.
  2. Select "Properties" on the popup menu. Windows will display a dialog containing the properties of the shortcut.
  3. The "Target" contains the command you want to modify. Copy that to the clipboard and paste it into Notepad. It will look something like this: 
      C:\python25\pythonw.exe "C:\Python25\Lib\site-packages\vespa\simulation\src\main.py"
  4. Change pythonw.exe to python.exe
  5. Save that file to C:\simulation.bat
  6. Open a command prompt (under Start/All Programs/Accessories/Command Prompt)
  7. Type C:\simulation.bat and hit enter. Windows will launch Simulation from the command prompt you started.

Messages sent to stdout will be visible in the command prompt.

OS X

  1. Start a command prompt (a.k.a "Terminal" in your Applications/Utilities folder).
  2. Paste in this command and hit enter: ~/Desktop/Simulation.command

Messages sent to stdout will be visible in the command prompt.

Linux

  1. The Desktop shortcut that launches Simulation is actually called Simulation.desktop (full path: ~/Desktop/Simulation.desktop). Open that file in a text editor.
  2. Find this line: 
      Terminal=false
  3. Change it to this: 
      Terminal=true
  4. Save your changes.
  5. Double click on the desktop shortcut to launch Simulation.

Messages sent to stdout will be visible in the command prompt that launches when you double click on the shortcut. Note that the command prompt will automatically close when you exit the application, so if you need to save what's displayed there, don't forget to save it into a text document before closing Simulation.