I want to calculate the center-of-mass using the map function. I don't want to use for loops. Help with bottom two lines?

```
class Obj():  
    def __init__(self, mass = 0., x = 0., y = 0.):    
        self.mass = mass    
        self.x = x    
        self.y = y    

# Create List of Objects    
objList = []
n = 0    
for i in range(0,10):    
    for j in range(0,10):    
        objList.append(Obj(i*j,i,j))    

# Calculate Center of Mass of List
# The following is pseudocode, does not actually work
SumOfMass = sum(objList[:].mass)       
CenterOfMassX = sum(objList[:].x.*objList[:].mass)/SumOfMass    

```