Doesn't run code when two key pressed

Question

func input(event):
if event.isactionpressed("uiup") && event.isactionpressed("uileft"): //doesn't work
// both have underscore [uiup,ui_left]

if event.isactionpressed("ui_up"): //worked

Answer 1

You're using event driven code; it won't fire for both events here (that is, including both events - likely one after the other). The event will hold one (and only one) input event (and/or modifiers, etc).

You could change the other check to Input, e.g.

if event.is_action_pressed("ui_up") && Input.is_action_pressed("ui_left"):
    # code

...and likewise for the ui_left event and pressed ui_up. Although I don't know what you're doing with the code here; likely you really want to apply some movement independently per frame; e.g. ui_up only applies some up value; ui_left some left; both should be applied when appropriate.