What's the best way of skip N values of the iteration variable in Python?

Question

In many languages we can do something like:

for (int i = 0; i < value; i++) {     if (condition)     {         i += 10;     } } 

How can I do the same in Python? The following (of course) does not work:

for i in xrange(value):     if condition:         i += 10 

I could do something like this:

i = 0 while i < value:   if condition:     i += 10   i += 1 

but I'm wondering if there is a more elegant (pythonic?) way of doing this in Python.

Answer 1

Use continue.

for i in xrange(value):     if condition:         continue 

If you want to force your iterable to skip forwards, you must call .next().

>>> iterable = iter(xrange(100)) >>> for i in iterable: ...     if i % 10 == 0: ...         [iterable.next() for x in range(10)] ...  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] [21, 22, 23, 24, 25, 26, 27, 28, 29, 30] [41, 42, 43, 44, 45, 46, 47, 48, 49, 50] [61, 62, 63, 64, 65, 66, 67, 68, 69, 70] [81, 82, 83, 84, 85, 86, 87, 88, 89, 90] 

As you can see, this is disgusting.

Answer 2

Create the iterable before the loop.

Skip one by using next on the iterator

it = iter(xrange(value)) for i in it:     if condition:         i = next(it) 

Skip many by using itertools or recipes based on ideas from itertools.

itertools.dropwhile()

it = iter(xrange(value)) for i in it:     if x<5:         i = dropwhile(lambda x: x<5, it) 

Take a read through the itertools page, it shows some very common uses of working with iterators.

itertools islice

it = islice(xrange(value), 10) for i in it:     ...do stuff with i...