[Python-ideas] Ruby-style Blocks in Python Idea

Steven D'Aprano steve at pearwood.info
Wed Mar 11 13:03:58 CET 2009

On Wed, 11 Mar 2009 11:01:41 am average wrote:

> These kind of [Anonymous] functions/code blocks explicitly tell the
> user that "This is NOT part of my program"

I'm a user, and they don't tell me any such thing.

By the way, that word, "explicitly" -- I think you are 
using "explicitly" as if it actually meant "implicitly". If the 
function were to explicitly tell the user, it would look something like 

caller( function_that_is_not_part_of_the_program x: x+1 )

which of course is ridiculously verbose. What you say might be true if 
lambda had that extended meaning, but it doesn't. In Python, lambda 
merely means "create a nameless function object from a single 

It's also nonsense, because there the function is, inside the program as 
clear as day. Arguing that a function that appears inside your program 
is not part of your program is rather like saying that your stomach is 
not part of your body.

Perhaps what you are getting at is that anonymous functions blur the 
difference between code and data, and that if you consider them as 
data, then they are outside the program in some sense? That's not 
entirely unreasonable: it's common to distinguish between code and 
data, even though fundamentally they're all just bits and, really, the 
distinction is all in our mind. (That doesn't mean the distinction 
isn't important.)

But even accepting that an anonymous function used as data is outside of 
the program in some sense, anonymity is strictly irrelevant. If you 
consider the lambda function here:

caller(lambda x: x+1)

to be data, then so is the named function foo here:

def foo(x):
    return x+1

> gibberish?

I'm trying to give you the benefit of the doubt.

Steven D'Aprano

More information about the Python-ideas mailing list