how to use X,Y from val(X,Y) in val_moyenne , how to use the return variable outside a function

def val_XY(fichier,num):     F=open(fichier,'r')     lines=F.readlines()     ...     return (X,Y) 

i want to use X and Y in this function for example :

def val_moyenne(X,Y):     Xm=sum(X)/len(X)     Ym=sum(Y)/len(Y)