[Tutor] Break element into list while iterating

[Peter Otten]

On 25/12/2021 18:11, Julius Hamilton wrote:
> Hey,
> 
> I would like to do some kind of list comprehension where elements meeting
> certain conditions get split on a delimiter. They don’t become lists nested
> in one element in the previous list; the new elements just get inserted
> where the old one was.
> 
> Like this:
> 
> [“apple”, “pear”]
> 
> ->
> 
> [“a”, “p”, “p”, “l”, “e”, “pear”]
> 
> Is there a list comprehension syntax where if I split an element with
> e.split(), I can “insert” those elements at the element they came from?

While you can solve this with a list comprehension...

 >>> [y for x in ["apple", "pear"] for y in (x if x == "apple" else [x])]
['a', 'p', 'p', 'l', 'e', 'pear']

I recommend a generator instead:

 >>> def explode_some(items, predicate, split):
     for item in items:
         if predicate(item):
             yield from split(item)
         else:
             yield item

 >>>
 >>> print(list(
     explode_some(
         ["apple", "pear"],
         lambda x: x == "apple",
         list
     )
))

['a', 'p', 'p', 'l', 'e', 'pear']

You'd probably inline the predicate() and split() functions unless you 
need them to be configurable in your actual use case.