Securing a future for anonymous functions in Python

Jeff Shannon jeff at
Thu Jan 6 19:23:36 EST 2005

Alan Gauld wrote:

> Can I ask what the objection to lambda is? 
> 1) Is it the syntax?
> 2) Is it the limitation to a single expression?
> 3) Is it the word itself?
> I can sympathise with 1 and 2 but the 3rd seems strange since a
> lambda is a well defined name for an anonymous function used in
> several programming languages and originating in lambda calculus
> in math. Lambda therefore seems like a pefectly good name to
> choose.

I think that the real objection is a little bit of 1), and something 
that's kinda close to 2), but has nothing to do with 3).

The issue isn't that lambdas are bad because they're limited to a 
single expression.  The issue is that they're an awkward special case 
of a function, which was added to the language to mollify 
functional-programming advocates but which GvR never felt really "fit" 
into Python.  Other, more pythonic functional-programming features 
have since been added (like list comprehensions and iterators).

It seems to me that in other, less-dynamic languages, lambdas are 
significantly different from functions in that lambdas can be created 
at runtime.  In Python, *all* functions are created at runtime, and 
new ones can be defined at any point in execution, so lambdas don't 
get that advantage.  Thus, their advantages are limited to the fact 
that they're anonymous (but names are treated differently in Python 
than in most other languages, so this is of marginal utility), and 
that they can be created inline.  This last bit makes them suitable 
for creating quick closures (wrapping a function and tweaking its 
parameters/return values) and for creating a delayed-execution object 
(e.g. callbacks), so there's a lot of pressure to keep them, but 
they're still a special case, and "special cases aren't special enough 
to break the rules".

Jeff Shannon
Credit International

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