1. 13
    Why 'd = {}' is faster than 'd = dict()' python blog.bordum.dk
    feoh avatar via feoh 9 months ago | cached | 7 comments

  1.  

  2. 2
    bwr avatar bwr 9 months ago | link

    I’m kinda confused - the graphs at the beginning seem to show the opposite of what the author is claiming. For a given number of executions, the shorthand (in blue) seems to take more time, not less. What am I missing?

    1. 4
      hwayne avatar hwayne 9 months ago | link

      Looks like the axes are flipped. The x-axis is actually time taken, and the y-axis is the number of executions. The labels are wrong, too: notice how it says the “number of executions” is 0.000001.

    2. 2
      nc avatar nc 9 months ago | link

      Why is this a surprise? Function calls will always have slight overhead, because of the indirection of a jump. That’s why inlining is a thing.

      1. 10
        apy avatar apy 9 months ago | link

        The surprising thing is I would expect {} to be syntactic sugar for dict().

        1. 3
          nc avatar nc 8 months ago | link

          Really? Since {} is recognized by the parser, I’d expect to generate the opcode directly as part of the bytecode compilation pass.

          Frankly, I’m surprised that dict() doesn’t compile to an opcode, since it’s easy to inline. I guess doing that would take away the ability to rebind what dict() does in the local scope (but I don’t know why anyone would care besides that).

          1. 7
            A-Za-z0-9 avatar A-Za-z0-9 edited 8 months ago | link

            You can even rebind it globally.

            $ python3
>>> dict({1: 2})
{1: 2}
>>> import builtins
>>> builtins.dict = list
>>> dict({1: 2})
[1]

            EDIT: use builtins instead of __builtins__, compare https://stackoverflow.com/questions/11181519/python-whats-the-difference-between-builtin-and-builtins

      2. 1
        nil avatar nil 8 months ago | link

        I’m pretty sure log10 casts to float before executing.