Sorry, this post is also filled with misinformation.

* The with-statement only causes the file to be closed after use. It has nothing to do with iteration.

* Files themselves are self-iterable (anything that loops over a file object uses a line-at-a-time iterator). Even writing "for line in f: ..." causes you to loop a line at a time without the whole file being in memory all at once.

* Sets are just one of many objects that takes an iterable as an argument: min(f), max(f), list(f), tuple(f), etc.