python: most elegant way to intersperse a list with an element
I would have written a generator myself, but like this:
def joinit(iterable, delimiter):
it = iter(iterable)
yield next(it)
for x in it:
yield delimiter
yield x
itertools to the rescue
- or -
How many itertools functions can you use in one line?
from itertools import chain, izip, repeat, islice
def intersperse(delimiter, seq):
return islice(chain.from_iterable(izip(repeat(delimiter), seq)), 1, None)
Usage:
>>> list(intersperse(666, ["once", "upon", "a", 90, None, "time"])
["once", 666, "upon", 666, "a", 666, 90, 666, None, 666, "time"]