From: Lie Ryan wrote:

In list/generator comprehension, currently we have no way to access the result of the expression and have to write something like this:

[f(x) for x in l if f(x) > 0]

if f() is heavy or non-pure (i.e. have side effects), calling f() twice might be undesirable.

I'm suggesting about something like:

[f(x) for x in l if @ > 0]

where @ is the result of the listcomp's expression (i.e. f(x))

Personally, I don't like the use of symbols like @, as python is not perl. I'm still thinking of a better syntax/approach and is open for suggestion.

What do you guys think?

I think it's a fine idea. The English language has evolved such a construct, typically used when one wants to highlight (rather than simply *refer* (as a pronoun does) to) the dominant noun without resorting to redundancy. [f(x) for x in l if same > 0] OR another possibility [f(x) for x in l if self > 0] obviously syntax highlighting makes this (or any keyword) standout better. Would be interesting to consider other usages for such a keyword addition (in the case of the former). Aahz:

Listcomps and genexps are like lambdas: run up against their limits and you should switch to a regular for loop or generator.

Generally decent advice, but there is value to exploring the Kolomogorov optimums for a given expressive need (compressing the highest amount of meaning in the simplest construction). In fact, I consider Python to be one of best languages in this regard (it's syntax being the evolution of programming-expressive compactness while being complete in itself. (In contrast to Perl, for example, which offloads the complexity to the programmer.) mark