So, I was watching Raymond Hettinger's talk Transforming Code into Beautiful, Idiomatic Python and he brings up this form of iter which I was never aware of. His example is the following: Instead of: blocks = [] while True: block = f.read(32) if block == '': break blocks.append(block) Use: blocks = [] read_block = partial(f.read, 32) for block in iter(read_block, ''): blocks.append(block) After checking the documentation of iter, I found a similar example: with open('mydata.txt') as fp: for line in iter(fp.readline, ''): process_line(line) This looks pretty useful to me, but I was wondering if of you Pythonistas know of any examples of this construct that doesn't involve I/O-read loops? Perhaps in the Standard Library? I can think of very contrived examples, like the following: >>> def f(): ... f.count += 1 ... return f.count ... >>> f.count = 0 >>> list(iter(f,20)) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19] >>> But obviously this is not any more useful that the built-in iterables. Also, it seems like code smell to me when you are assigning state to a function. At that point, I'd likely should be working with a class, but if I'm going to write a class, I might as well implement the iterator protocol for whatever I want to accomplish. Continue reading...
