On Sat, Jan 25, 2014 at 12:41 AM, Greg Ewing <greg.ewing@canterbury.ac.nz> wrote:

Brett Cannon wrote:

On Fri, Jan 24, 2014 at 10:50 AM, Ram Rachum <ram@rachum.com <mailto:ram@rachum.com>> wrote:

lambda (x, y): whatever

http://python.org/dev/peps/pep-3113/

Part of the rationale in that PEP is that argument unpacking
can always be replaced by an explicitly named argument and
an unpacking assignment. No mention is made of the fact that
you can't do this in a lambda, giving the impression that
lambdas are deemed second-class citizens that are not worth
consideration.

The author was clearly aware of the issue, since a strategy
is suggested for translation of lambdas by 2to3:

lambda (x, y): x + y --> lambda x_y: x_y[0] + x_y[1]

That's a bit on the ugly side for human use, though.
An alternative would be

lambda xy: (lambda x, y: x + y)(*xy)

Whether that's any better is a matter of opinion.

As the author of the PEP and I can say that `lambda (x, y): x + y` can just as easily be expressed as `lambda x, y: x + y` and then be called by using *args in the argument list. Anything that gets much fancier typically calls for a defined function instead of a lambda.