Most unreadable 1-Liner - just for fun!
class Solution:\n\n    def __init__(self, rects: List[List[int]]):\n        self.W = list(itertools.accumulate((x[2]-x[0]+1)*(x[3]-x[1]+1) for x in rects))\n   
```class Solution:\n\n    def __init__(self, rects: List[List[int]]):\n        self.W = list(itertools.accumulate((x[2]-x[0]+1)*(x[3]-x[1]+1) for x in rects))\n        self.rects = rects\n\n    def pick(self) -> List[int]:\n        return [(xr:=random.randint)((c := self.rects[(ans := bisect.bisect_left(self.W,xr(0,self.W[-1]) ))])[0],c[2]),xr(c[1],c[3])]\n```
['Python3']