On 2016-06-30 09:59, Steven D'Aprano wrote:
> But there's no need to go to such effort for a mutable iterator.
> This is much simpler:
>
> py> mi = list('bananas')
> py> for char in mi:
> ... if char == 'a':
> ... mi.extend(' yum')
> ... print(char, end='')
> ... else: # oh no, the feared for...else!
> ... # needed to prevent the prompt overwriting the output
> ... print()
> ...
> bananas yum yum yum
> py>
>
>
> This example shows two things:
>
> (1) There's no need for a MutableIterator, we have list;
Convenient to know. I was fairly certain that this had failed for me
in past versions, but I went back to the oldest I have (2.4) and it
still works there. Might have to revisit some queuing code I have.
That said, it's not consistent across iterable container types. With
mi = set('bananas')
for char in mi:
if char == 'a':
mi.add('X')
print(char)
else:
print()
I get
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError: Set changed size during iteration
If the list() meets your needs, then you're in luck. But just as
frequently, I want to use a set() or a dict() and have to write my
own wrapper around it.
-tkc
--
https://mail.python.org/mailman/listinfo/python-list
