pythonic way to iterate over part of a list

python list iteration
Claudiu picture Claudiu · Dec 29, 2011 · Viewed 47.3k times · Source

I want to iterate over everything in a list except the first few elements, e.g.:

for line in lines[2:]:
    foo(line)

This is concise, but copies the whole list, which is unnecessary. I could do:

del lines[0:2]
for line in lines:
    foo(line)

But this modifies the list, which isn't always good.

I can do this:

for i in xrange(2, len(lines)):
    line = lines[i]
    foo(line)

But, that's just gross.

Better might be this:

for i,line in enumerate(lines):
    if i < 2: continue
    foo(line)

But it isn't quite as obvious as the very first example.

So: What's a way to do it that is as obvious as the first example, but doesn't copy the list unnecessarily?

Answer

soulcheck picture soulcheck · Dec 29, 2011

You can try itertools.islice(iterable[, start], stop[, step]):

import itertools
for line in itertools.islice(list , start, stop):
     foo(line)

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