ImportError in eric4

[rhill]

I am new to Linux/Python/Eric4 (not in development though).

So I am trying to start a small application as per tutorial found at 
eric-ide.python-projects.org:

http://eric-ide.python-projects.org/tutorials/LogParser/chap1.html

My application is similarly structured. Final step, I try to execute it 
(Run Project...), and I get:

/=====
The debugged program raised the exception unhandled ImportError
"No module named ui.MainWindow"
File: /home/xxx/xxx/my first project/main.py, Line: 4
Break here?
\=====

Here is the content of main.py:

/=====
#!/usr/bin/python
		
from PyQt4.QtGui import QApplication
from ui.MainWindow import MainWindow

def main():
     import sys
     app = QApplication(sys.argv)
     wnd = MainWindow()
     wnd.show()
     sys.exit(app.exec_())

if __name__ == '__main__':
     main()
\=====

As per tutorial. The file MainWindow.py *really* exists, and is *really* 
located inside the folder 'ui' which itself is inside 'my first project' 
(the root of the project I am working on.)

I couldn't find anything meaningful help through google, so here I am.

Why is the file ./ui/MainWindow.py not seen by the python interpreter?