explain this function to me, lambda confusion

[Lie]

On May 9, 12:12 pm, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
wrote:
> En Thu, 08 May 2008 22:57:03 -0300,  
> <andrej.panj... at climatechange.qld.gov.au> escribió:
>
>
>
> > On May 8, 6:11 pm, Duncan Booth <duncan.bo... at invalid.invalid> wrote:
>
> >> No, no, no, no, no!
> > Geez.  Go easy.
> >> You have got it entirely wrong here. Your XOR function simply
> [...]
> > Pardon my tetchiness, but it is a little hard to receive such blunt
> > and inflexible replies to my posts.
>
> Don't take it so seriously. I would have written a reply in the same tone.  
> Weeds must be uprooted early :)
>
> > Both the responses offer lambda free alternatives.  That's fine, and
> > given the terse documentation and problems that I had understanding
> > them, I would agree.  So what applications are lambdas suited to?  I
> > think the parameterised function model is one.
> > What else?
>
> It should be clear now that lambda is just a shortcut for defining a  
> normal function using "def", except it has no name, and it can handle  
> expressions only (no statements).
> So you never *need* a lambda. But in a few cases they're useful:
>
> - Most GUIs are event-driven, and let you bind a function (or any other  
> callable object) to be executed when certain event happens (by example,  
> when certain button is pressed, or a menu item is selected). Usually an  
> instance method is used: Button("Total", onclick=self.calculate_total).  
> Suppose you're developing a calculator; the ten buttons labeled '0' to '9'  
> should inserte the corresponding digit. To do that, you should write ten  
> functions insert_digit_0 to insert_digit_9 (and they would be  
> one-line-functions: insert_digit('0') ... insert_digit('9')). Too boring :(
> The usual idiom is something like this:
>      Button("0", onclick=lambda: self.insert_digit('0'))
>      Button("5", onclick=lambda: self.insert_digit('5'))
>
> - To write an expression that is to be evaluated lazily (perhaps only if  
> certain other conditions are met). Older Python versions didn't have a  
> conditional expression like C's :? ternary operator, and one possible way  
> to emulate it is this:
>
> def iif(cond, if_true, if_false):
>      if cond:
>          return if_true()
>      else:
>          return if_false()
>
> iff(x!=2, lambda: 1/(x-2), lambda: 100)
>
> You can't write iff(x!=2, 1/(x-2), 100) because arguments are evaluated  
> before the function is called, and with x=2 you get an error.
>

Calling iff would give a NameError. I wonder why... perhaps because
iif is so iffy?