List Flatten

[bearophile]

Comparing versions for speed, Raymond Hettinger's version is quite
slow (even 10 or more times slower than mine for certain kinds of
lists).

Into the most nested cicle of Alex Martelli's version there is a
function call to isatomic (and the try-except) that slow down the
program a lot. Removing them (we expand lists only) we obtan the short
Peter Otten's version, that is a bit better than mine for very nested
lists and a bit worse for quite flat lists (that are the most common,
I think).

Thank you all,
bear hugs,
bearophile