"yield from iterable" vs "return iter(iterable)"

The only significant difference is what happens when an exception is raised from within the iterable. Using return iter() your FancyNewClass will not appear on the exception traceback, whereas with yield from it will. It is generally a good thing to have as much information on the traceback as possible, although there could be situations where you want to hide your wrapper.

Other differences:

• return iter has to load the name iter from globals - this is potentially slow (although unlikely to significantly affect performance) and could be messed with (although anyone who overwrites globals like that deserves what they get).

• With yield from you can insert other yield expressions before and after (although you could equally use itertools.chain).

• As presented, the yield from form discards any generator return value (i.e. raise StopException(value). You can fix this by writing instead return (yield from iterator).

Here's a test comparing the disassembly of the two approaches and also showing exception tracebacks: http://ideone.com/1YVcSe

Using return iter():

  3           0 LOAD_GLOBAL              0 (iter)              3 LOAD_FAST                0 (it)              6 CALL_FUNCTION            1 (1 positional, 0 keyword pair)              9 RETURN_VALUETraceback (most recent call last):  File "./prog.py", line 12, in test  File "./prog.py", line 10, in iRuntimeError

Using return (yield from):

  5           0 LOAD_FAST                0 (it)              3 GET_ITER              4 LOAD_CONST               0 (None)              7 YIELD_FROM              8 RETURN_VALUETraceback (most recent call last):  File "./prog.py", line 12, in test  File "./prog.py", line 5, in bar  File "./prog.py", line 10, in iRuntimeError