python equivalent of T(x,y)=(x*y,x+y) ?

edit

I don't know if this is what you are looking for, but the Sage preparser can tell you exactly what is done in Python behind the scenes:

sage: preparse('T(x,y) = (x*y,x+y)')
'__tmp__=var("x,y"); T = symbolic_expression((x*y,x+y)).function(x,y)'

This is not an answer, but I need more room for my text.

I think that what Shu wants is the following :

#! /usr/bin/sage -python
# -*- coding: utf8 -*-

from sage.all import *
var('x,y')
T = (x+y,x*y)  # (1)
print T.diff() # (2)

But the execution of that code finishes on :

AttributeError: 'tuple' object has no attribute 'diff'

Thus the question is : how to modify the line (1) in order the line (2) to produce that answer :

[(x, y) |--> y (x, y) |--> x]
[(x, y) |--> 1 (x, y) |--> 1]