How to catch an exception in the for loop iterator

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If your inner iterable can be continued after an exception, all you need to wrap it is a trivial generator:

def wrapper(gen):
  while True:
    try:
      yield next(gen)
    except StopIteration:
      break
    except Exception as e:
      print(e) # or whatever kind of logging you want

For example:

In [9]: list(wrapper(csv.reader(open('test.csv', 'r'))))
field larger than field limit (10)
Out[9]: [['foo', 'bar', 'baz'], ['abc', 'def', 'ghi']]

On the other hand, if the inner iterator can’t be continued after an exception, there’s no way you can wrap it:

def raisinggenfunc():
    yield 1
    raise ValueError("spurious error")
    yield 3

In [11]: list(wrapper(raisinggenfunc()))
spurious error
Out[11]: [1]

Any generator created by calling a Python generator function or evaluating a generator expression will not be resumable.

In such a case, you need to find some way to create a new iterator that resumes iteration. For something like csv.reader, that would mean reading n lines from the file before wrapping it in a csv.reader. In other cases it might mean passing n to the constructor. In other cases—as with raisinggenfunc above, it’s just not possible.

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