Could you explain lambda function to me?

[ast]

"fl" <rxjwg98 at gmail.com> a écrit dans le message de 
news:323866d1-b117-4785-ae24-7d04c49bc063 at googlegroups.com...
> Hi,
>
>>>> def make_incrementor(n):
> ...     return lambda x: x + n
> ...
>>>> f = make_incrementor(42)
>>>> f(0)
> 42
>>>> f(1)
> 43

make_incrementor is a fonction which return a function !
and the returned function just add n to its input

it is equivalent to:

def make_incrementor(n):

    def inc(x):
        return x+n

    return inc

>
>
> The second lambda example is even more obscure to me:
>
>>>> pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')]
>>>> pairs.sort(key=lambda pair: pair[1])
>>>> pairs
> [(4, 'four'), (1, 'one'), (3, 'three'), (2, 'two')]
>
>
> Could you explain 'key=lambda pair: pair[1]' to me?

the sort is done on the values returned by the key function
key function "lambda pair: pair[1]" returns the second element of each pair ( , )

so the sort is done alphabetically on the strings 'one' 'two' 'three' 'four'