How can I see at which index my iterator is?

Question

So I have a string source, over which I loop with an iterator:

iterator = iter(source)
for char in iterator:
  do stuff

However, now say that I have a check in do stuff, where I compare the value of the iterator to 'h'. Then I want to see if the 'h' is followed by "ello ", in some way, and add the first ten characters after that to a list.
For this my own idea would be to find out which index corresponds with the current position of the iterator, so that I can say:

indIt = index(char)
if source[indIt + 1: indIt + 6] == "ello ":
  someList.append(source[indIt + 7:indIt + 16])
  indIt += 17
  char = indIt #which may also be fun to know how it can be done, if

This would mean that for given input hello Sandra, oh and hello Oscar, i welcome you both!, someList would contain ["Sandra, oh", "Oscar, i w"].

So can I, in some way, figure out to which index the current position of an iterator corresponds?

@ppperry: What's wrong with [`enumerate()`](https://docs.python.org/2.3/whatsnew/section-enumerate.html)? — zondo, May 15 '16 at 12:47

score 6 · Accepted Answer · answered May 15 '16 at 12:48

Iterators don't expose an index, because there doesn't have to be a sequence underlying one.

Use the enumerate() function to add one to your iteration:

for index, char in enumerate(iterator):

Now iteration produces (index, value) tuples, which you can assign to two separate variables using tuple assignment.

How can I see at which index my iterator is?

1 Answers1