Iteration, while loop, and for loop

Tim Chase python.list at tim.thechases.com
Tue Jun 28 13:23:08 EDT 2016


On 2016-06-29 01:20, Steven D'Aprano wrote:
> While loops are great for loops where you don't know how many
> iterations there will be but you do know that you want to keep
> going while some condition applies:
> 
> while there is still work to be done:
>     do some more work

I find this particularly the case when the thing being iterated over
can be changed, such as a queue of things to process:

  items = deque()
  items.append(root_node)
  while items:
    item = items.popleft()
    process(item)
    items.extend(item.children)

Using a "for" loop balks if you try to change the thing over which
you're iterating.

But then, if you wrap up your "while" loop as a generator that yields
things, you can then use it in a "for" loop which seems to me like
the Pythonic way to do things. :-)

-tkc





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