how to iterate over several lists?

[kj]

Suppose I have two lists, list_a and list_b, and I want to iterate
over both as if they were a single list. E.g. I could write:

for x in list_a:
foo(x)
for x in list_b:
foo(x)

But is there a less cumbersome way to achieve this? I'm thinking
of something in the same vein as Perl's:

for $x in (@list_a, @list_b) {
foo($x);
}

TIA!

kynn

--

 

[Chris Rebert]

Suppose I have two lists, list_a and list_b, and I want to iterate
over both as if they were a single list.  E.g. I could write:

for x in list_a:
   foo(x)
for x in list_b:
   foo(x)

But is there a less cumbersome way to achieve this?  I'm thinking
of something in the same vein as Perl's:

for $x in (@list_a, @list_b) {
 foo($x);
}

Just add the lists together.

for x in list_a + list_b:
foo(x)

Cheers,
Chris

 

[kj]

Just add the lists together.

for x in list_a + list_b:
foo(x)

Cool! Thanks!

kynn
--

 

[Stefan Behnel]

Suppose I have two lists, list_a and list_b, and I want to iterate
over both as if they were a single list. E.g. I could write:

for x in list_a:
foo(x)
for x in list_b:
foo(x)

But is there a less cumbersome way to achieve this?

Take a look at the itertools module, especially itertools.chain().

Stefan

 

[Minesh Patel]

def chain(*args):
 return (item for seq in args for item in seq)

for x in chain(list_a, list_b):
   foo(x)

If they are the same length, you can try the zip built-in function.

 

[Chris Rebert]

If they are the same length, you can try the zip built-in function.

But he doesn't want to iterate over them in parallel...

Cheers,
Chris

 

[Steven D'Aprano]

If they are the same length, you can try the zip built-in function.

Which does something *completely different* from what the Original Poster
was asking for.

Given alist = [1, 2, 3], blist = [4, 5, 6], the OP wants to process:

1, 2, 3, 4, 5, 6

but zip will give:

(1, 3), (2, 5), (3, 6)