重新編寫for循環的功能，需要幫助更好地瞭解

Question

我是新來的蟒蛇，我需要幫助，重新寫，對循環功能有缺口下方

y = [g(x,y) for x in xs for y in xs if f(x,y)] 

完整的代碼是在這裏

g = lambda x,y:(x-y) 
f = lambda x,y: x>y 
xs = [1,2,3,4] 
y = [g(x,y) for x in xs for y in xs if f(x,y)] 

Answer 1

y = [] 
for a in xs: 
    for b in xs: 
     if f(a, b): 
      y.append(g(a, b))