lambda (x, y): x + yis no longer possible in Python 3000. You are supposed to write
lambda x_y: x_y + x_yinstead. This also applies to functions, not just to lambdas and the idea belongs to PEP 3113 which forbids automatic tuple unpacking in function parameters. Ugly and inconvenient if you ask me, but there apparently was somebody who kept shooting himself in the leg.
I think that automatic unpacking was rather useful (if used sparingly), especially when you had to do something like
map(lambda (i, (a, b)): i * (a + b),which is now what ?
map(lambda i_a_b: i_a_b * (i_a_b + i_a_b),Eeew...