Comments on Jarrod Millman: What's the best way to interleave two Python lists...

Since you liked zip, why not to like reduce (altho...

2010-10-13T17:44:12.117-07:00

Since you liked zip, why not to like reduce (although iirc Guido doesn't like it ;-)), so for the actual interleave just use both functions you would like:

*In [1]: reduce(tuple.__add__, zip([1,2],[11,21]))
Out[2]: (1, 11, 2, 21)

?

I would use itertools.chain: from itertools impor...

2010-10-11T13:25:09.604-07:00

I would use itertools.chain:

from itertools import chain

a = list('abcde')
b = list('12345')

list(chain(*zip(a,b)))

['a', '1', 'b', '2', 'c', '3', 'd', '4', 'e', '5']

It can be extended to merge more than two lists:

c = list('XYZZY')
list(chain(*zip(a,b,c)))

If the lists are long, or are iterables, or you want to merge the lists lazily, use iterttools.izip:

from itertools import chain, count, izip

for value in chain(*izip(count(),a+b+c)):
print value

another variation of solution 7: reduce(lambda ou...

2010-10-11T03:52:40.521-07:00

another variation of solution 7:

reduce(lambda out, p: out + [p, p+'64'], paths, list())

Or using a bit from the previous comment (and rela...

2010-10-11T01:41:32.844-07:00

Or using a bit from the previous comment (and relating it to your example):

out = []
map(out.extend,([p, p + '64'] for p in paths))

Here's another simple one (note that you are t...

2010-10-11T01:36:17.672-07:00

Here's another simple one (note that you are throwing away the result of the map statement).

1> A = [1,2,3,4,5]
2> B = [6,7,8,9,10]
3> out = []
4> map(out.extend,zip(A,B))
<4> [None, None, None, None, None]
5> out
<5> [1, 6, 2, 7, 3, 8, 4, 9, 5, 10]

Good thing there's only one way to do it with ...

2010-10-10T15:14:58.410-07:00

Good thing there's only one way to do it with Python... :-)

A variation of solution 6: [item for items in (...

2010-10-10T14:35:55.494-07:00
A variation of solution 6:
[item for items in ([p, p + '64'] for p in paths) for item in items]. No need for the zip just use a generator expression.

I also like solutions 5 as a general solution, tho...

2010-10-10T06:51:49.180-07:00
I also like solutions 5 as a general solution, though stylistically, I prefer "map(out.extend, ([p, p + '64'] for p in paths))" to the for loop. I think yours is the more pythonic solution (and might even be more efficient). I like to use map if all a for loop does is call a function on each element of an iterable, since I think it's a bit clearer and it saves a line of code.

Another solution (a modification of solution 7) is "return sum(([p, p + '64'] for p in paths), [])", which saves an import. I'd probably go with that since it's shorter, and efficiency only matters if the lists are extremely long or this function gets called a lot, neither of which is true in your application.