On 03/11/2020 13:13, duncan smith wrote:
On 02/11/2020 19:09, dn wrote:
On 02/11/2020 23:29, Bischoop wrote:
On 2020-11-01, duncan smith <duncan@invalid.invalid> wrote:
But this generates the letters counts for each word. They only need to
be generated once (outside the for loop). And using count requires
iterating over the letters / words for each x in letters (rather than
once). For a large enough collection of words you'd notice the
difference.
Multiple loops written in Python are likely to be slower than same in
compiled code - which was probably part of the motivation for @Terry's
response. Plus, "re-use" - why write something ourselves if someone else
has already done the work?
...
- str.find() or .index() will locate a character within the string...
But he appears to need the count in order to compare against the counts
in letters. I assume letters could be something like 'att', in which
case knowing a word contains more than one 't' doesn't cut it. He could
try iterating over the characters in each word once, checking that no
count from letters is exceeded, and that the number of remaining
characters gives some chance that the relevant counts from letters could
be achieved. In the worst case (e.g. a conforming word) this requires
iterating over all the characters in a word once. That's not to say it
would actually run quicker 'on average' than a solution using Counter.
The str.index() idea solves both (ie "all") examples given, but beyond
that, no guarantees!
The (full) specs are not clear. There's certainly room for
misunderstanding. I'd be happier if I could 'see' a full spec or
recognise a practical application, because then we'd be better able to
discuss facts. Meantime, we try to help with what we have been given...
The OP's sample code only realises "conforming word[s]" (good term
BTW!). The snippet does not report any "count". Similarly, there's no
facts to avoid ("I assume") an assumption about whether "Letters" may
include duplication - indeed: whether duplication has meaning or should
be regarded as user-error.
The point has been made that finding multiple instances of "Letters"
disqualifies that word. Does that (also) disqualify having repetition
of a letter within Letters? (or not?)
What does "att" imply? That there must be one and only one "a" in the
word, plus a "t", and only one *other* "t"? Can't see it in 'the specs'
to be able to say "right" or "wrong"! (Nor is it my spec!)
Whereas the OP indicates (first example) that the two characters "a" and
"t" must appear, there was no apparent, required, linkage (or
separation) between them, eg "auto" doesn't include the two letters
consecutively (one of my first (mistaken) thoughts when looking at the OP).
Accordingly, I (again, rightly or wrongly), assumed that the lack of
linkage between characters in "Letters" reasonably suggested (if not,
implied) that if "auto" matches "at", it would also match "ta".
Similarly, and without further detail, I couldn't see good reason why
Letters itself would contain repetition, eg "att". (or not!)
Aside: that idea might make for a good second-level challenge!
(complicating both the nested-loops and the str.index() ideas - but
possibly not when using counter()...)
When counter() was suggested, it was necessary to 'count' the characters
in both the candidate-word and "Letters". Isn't that 'requirement'
necessary only to be able to perform the final comparison/validation
step? (there is no equivalent in the .index() algorithm)
Whereas counter() was mentioned as a potential solution, it didn't seem
to fit. So, I sought another...
Moving to the suggested speed-comparison (and lesson in drawing from
Python's rich collection of resources) was originally aimed at putting a
native-Python nested list string manipulation solution, alongside an
embedded function alternative. (cf anything involving Counter)
- but hey, "the more the merrier..."!
Performing this sort of experiment, and making such an observation (for
oneself) is a great motivator (should one be needed) to learn Python's
built-in functions, what is available in the PSL, and locating other
similar 'riches' offered within the Python 'eco-system'!
--
Regards =dn
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