Nuke Python Expression Switch
Nuke’s Python expression syntax can be shorter and more readable than tcl.
Imagine, you want to use a switch to toggle part of your comp on or off on certain frames – maybe to fix artifacts in a 3D pass. Instead of animating a switch’s input or a tool’s mix slider between 0 and 1 you could use an expression:
frame == 1025
This will set the knob to 1 on frame 1025 and to 0 anywhere else. An expression like that also works if you want to enable that knob on several frames, but it gets increasingly unreadable:
frame == 1025 || frame == 1072 || frame == 1074
A Python expression is shorter and easier to extend. Enable the Py button in the expression popup and there you go:
nuke.frame() in [1025,1072,1074]