Abreviation of practical work assignment?
Yes, lab is frequently used as a term to denote a medium size assignment. Exercise would be used for a shorter one, and project for something more extensive. 

But the terminology isn't standardized so you can use your own terms, as long as the reader understands them. 

But I'll also note, that just as in programming it isn't the typing that makes writing hard, so, IMO, abbreviations have limited utility and are often counterproductive. Written work is normally, and appropriately, a bit more formal than conversational work. This is due to the fact that the audience is wider and you don't know as much about it. So clarity over brevity should probably be valued.