[Python-Dev] any support for a methodcaller HOF?

Giovanni Bajo rasky at develer.com
Fri Feb 3 20:05:42 CET 2006

Robert Brewer <fumanchu at amor.org> wrote:

> The word "execution" to me implies "statements", and
> although some functions somewhere are called behind the scenes to
> evaluate any expression, the lambda (and its potential successors)
> differ from "def" by not allowing statements. They may be used to "defer
> execution" but to me, their value lies in being static
> expressions--object instances which are portable and introspectable.

> This is where LINQ [1] is taking off: expressions are declared with
> "var" (in C#). I used Expression() in Dejavu [2] for the same reasons
> (before LINQ came along ;), and am using it to build SQL from Python
> lambdas. I had to use lambda because that's Python's only builtin
> support for expressions-as-objects at the moment, but I'd like to see
> Python grow a syntax like:
>     e = expr(x: x + 1)

I see what you mean, but in a way you're still agreeing with me :) Your
expression-as-objects proposal is very clever, but to me (and as far as this
thread is concerned) it still allows to write a "decorated" piece of code
(expression), pass it around, and execute (evaluate) it later. This is what
I (and others) mainly use lambda for, and your expr() thing would still
serve me well. Instead, itemgetter() and friends are going to a different
direction (the expression which is later evaluated is not clearly expressed
in familiar Python terms), and that's what I find inconvenient.
Giovanni Bajo

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