What’s the smart way to pick any arbitrary number of items with XSI’s PickElement or PickObject commands? Read below… 😀
si = Application
def pickForever(**kwargs):
'''
Pick forever, and ever, and ever, and ever...
until you rightclick.
'''
# Default options
leftMessage = kwargs.setdefault('leftMsg', 'Pick something')
middleMessage = kwargs.setdefault('middleMsg', leftMessage)
selFilter = kwargs.setdefault('selFilter', 'object')
# Loop and yield forever until complete:
while 1:
out = si.PickElement(selFilter, leftMessage, middleMessage)
obj = out("PickedElement")
buttonPressed = out("ButtonPressed")
modifier = out("ModifierPressed")
if obj:
yield obj, buttonPressed, modifier
else:
break
# _______________________________________
# USAGE EXAMPLES:
def processIndividually():
'''
Deal with each pick, one object at a time...
'''
for obj, button, modifier in pickForever(leftMsg='Pick Object', selFilter='polygonmesh'):
button = ['left','middle'][button-1]
# (-1 because 0 means right, but is never returned.)
si.LogMessage( "Picked %s with your %s mouse button!" % (obj.FullName, button) )
def listExample():
'''
Getting a list of picked objects, only after picking is complete...
'''
pickedObjects = zip(*list( pickForever(leftMsg='Pick Object') ))[0]
si.LogMessage( pickedObjects )
# Cool, eh? :)
How or why does this work? What the heck is yield doing?
In Python, you can think of a “yield” statement like a “return” one, except it doesn’t finish the function evaluation.
A function using yield will act as a “generator“, returning one thing at a time each time it is called, until it stops yielding. (In our snippet, returning one tuple containing three pieces of data.) When iterating/looping in Python, when nothing is returned it stops, therefore when a yielding function stops returning, the loop ends.
Hat tip to Xavier Lapointe for originally showing me the trick and to Patrick Boucher for helping me remember the yield logic.