"Owain Clarke" <[email protected]> wrote
I would love a really clear explanation of lambda!
lambda returns an anonymous function - a function without a name.
When we define a function normally we use something like:
def square(x):
return x*x
That creates a function that has the name square
We can do the same with lambda:
square = lambda x : x*x
which is equivalent to the def form.
This is useful where we only need the function
temporarily, such as to return a sort key or in
building GUI controls.
The general shape of lambda is:
lambda <parameter list> : <return expression>
So in your case
lambda x: x[0]
could be replaced with
def first(x): return x[0]
lst.sort(key=first)
But since you don't use first() for anything else
you don't really need a named function so you
can use a lambda. lambda is best used for
short single line functions. In fact you can only
use it where the body of the function can be
expressed as a single expression.
You will find more explanation and examples
in the Functional Programming topic in my tutorial.
HTH
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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