def dependent(a, b):
 if pspace_independent(a, b):
  return False
 z = Symbol('z', real=True)
 return ((density(a, Eq(b, z)) != density(a)) or (density(b, Eq(a, z)) != density(b)))

def dependent ( a , b ) : if pspace_independent ( a , b ) : return False z = Symbol ( 'z' , real = True ) return ( ( density ( a , Eq ( b , z ) ) != density ( a ) ) or ( density ( b , Eq ( a , z ) ) != density ( b ) ) )
dependence of two random expressions two expressions are independent if knowledge of one does not change computations on the other .