On 9/26/07, Terry Jones wrote:

What's the most compact way to repeatedly call a function on a list without accumulating the results?

While I can accumulate results via

a = [f(x) for x in mylist]

or with a generator, there doesn't seem to be a way to do this without accumulating the results. I guess I need to either use the above and ignore the result, or use

for x in mylist: f(x)

I run into this need quite frequently. If I write

[f(x) for x in mylist]

with no assignment, will Python notice that I don't want the accumulated results and silently toss them for me?

Only after the list is completely constructed. List comprehensions are literally 'for' loops with an append call to a method so without extending the peepholer to notice this case and strip out the list creation and appending it is not optimized.

A possible syntax change would be to allow the unadorned

f(x) for x in mylist

And raise an error if someone tries to assign to this.

Go with the 'for' loop as Adam suggested. I just don't see this as needing syntax support. -Brett

On Wed, September 26, 2007 10:42 pm, Terry Jones wrote:

What's the most compact way to repeatedly call a function on a list without accumulating the results?

While I can accumulate results via

a = [f(x) for x in mylist]

or with a generator, there doesn't seem to be a way to do this without accumulating the results. I guess I need to either use the above and ignore the result, or use

for x in mylist: f(x)

I run into this need quite frequently. If I write

[f(x) for x in mylist]

with no assignment, will Python notice that I don't want the accumulated results and silently toss them for me?

A possible syntax change would be to allow the unadorned

f(x) for x in mylist

And raise an error if someone tries to assign to this.

If you want to do it like this, why not do it explicitly: def exhaust(iterable): for i in iterable: pass Then you can write: exhaust(f(x) for x in mylist) Done! -- Arnaud