Diagon Lemmy
  • Communities
  • Create Post
  • Create Community
  • heart
    Support Lemmy
  • search
    Search
  • Login
  • Sign Up
@abhi9u@lemmy.world to Technology@lemmy.worldEnglish • 2 months ago

Python Performance: Why 'if not list' is 2x Faster Than Using len()

blog.codingconfessions.com

external-link
message-square
135
fedilink
192
external-link

Python Performance: Why 'if not list' is 2x Faster Than Using len()

blog.codingconfessions.com

@abhi9u@lemmy.world to Technology@lemmy.worldEnglish • 2 months ago
message-square
135
fedilink
Discover why 'if not mylist' is twice as fast as 'len(mylist) == 0' by examining CPython's VM instructions and object memory access patterns.
  • @gravitas_deficiency@sh.itjust.works
    link
    fedilink
    English
    3•2 months ago

    My point is that the second statement you presented can have the effect of evaluating emptiness of a Sequence (note: distinct from an Iterable), but that only holds true if the target of the conditional IS a sequence. I’m underlining the semantic difference that was elided as a result of falsey evaluation.

    • @JasonDJ@lemmy.zip
      link
      fedilink
      English
      1•2 months ago

      Ok, help a noob out. What is the difference between a sequence and an iterable? Is a sequence immutable, like a tuple?

      • @gravitas_deficiency@sh.itjust.works
        link
        fedilink
        English
        1•
        edit-2
        2 months ago

        thing: Sequence[Any] iirc is iterable, indexable, and reversible.

        thing: Iterable[Any] only guarantees that its iterable - and note that iterating can sometimes have the effect of consuming the iterable (e.g. when working with streaming interfaces)

      • @48954246@lemmy.world
        link
        fedilink
        English
        1•2 months ago

        An iterable is just something that can be iterated over, like range(10), or [1, 2, 3].

        A sequence on the other hand is a Collection that is reversible.

        https://docs.python.org/3/library/collections.abc.html#collections-abstract-base-classes

        • @gravitas_deficiency@sh.itjust.works
          link
          fedilink
          English
          1•2 months ago

          I know what an iterable is. But I am talking about Type[Iterable], which iirc does not obey falsey eval when empty.

Technology@lemmy.world

!technology@lemmy.world

Subscribe from Remote Instance

Create a post
You are not logged in. However you can subscribe from another Fediverse account, for example Lemmy or Mastodon. To do this, paste the following into the search field of your instance: !technology@lemmy.world

This is a most excellent place for technology news and articles.


Our Rules


  1. Follow the lemmy.world rules.
  2. Only tech related news or articles.
  3. Be excellent to each other!
  4. Mod approved content bots can post up to 10 articles per day.
  5. Threads asking for personal tech support may be deleted.
  6. Politics threads may be removed.
  7. No memes allowed as posts, OK to post as comments.
  8. Only approved bots from the list below, this includes using AI responses and summaries. To ask if your bot can be added please contact a mod.
  9. Check for duplicates before posting, duplicates may be removed
  10. Accounts 7 days and younger will have their posts automatically removed.

Approved Bots


  • @L4s@lemmy.world
  • @autotldr@lemmings.world
  • @PipedLinkBot@feddit.rocks
  • @wikibot@lemmy.world
  • 4.71K users / day
  • 10.3K users / week
  • 17.4K users / month
  • 37.5K users / 6 months
  • 71.5K subscribers
  • 9.96K Posts
  • 296K Comments
  • Modlog
  • mods:
  • @L3s@lemmy.world
  • enu
  • Technopagan
  • L4sBot
  • L3s
  • @L4s@hackingne.ws
  • BE: 0.19.3
  • Modlog
  • Instances
  • Docs
  • Code
  • join-lemmy.org