what does := means simply?

[bartc]

On 18/05/2018 15:47, Chris Angelico wrote:
> On Sat, May 19, 2018 at 12:37 AM, bartc <bc at freeuk.com> wrote:
>> Have a look at some of the implementations here (to test some Mandelbrot
>> benchmark):
>>
>> https://benchmarksgame-team.pages.debian.net/benchmarksgame/performance/mandelbrot.html
>>
>> The three Python examples all use 'import sys' and 'import multiprocessing',
>> none of which I can find any trace of as any sort of files let alone .py.
>> One of them also uses 'import array', which I can't find either.
> 
> I guess you didn't look very hard.
> 
>>>> import multiprocessing
>>>> multiprocessing.__file__
> '/usr/local/lib/python3.8/multiprocessing/__init__.py'

But you have to load it first to find out. (And if you follow nested 
imports, you will eventually get to those that don't have a .py file.)

>>>> import array
>>>> array.__file__
> '/usr/local/lib/python3.8/lib-dynload/array.cpython-38m-x86_64-linux-gnu.so'

I get "module 'array' has no attribute '__file__'".

However, if I load sys, multiprocessing and array, then print 
sys.modules, I get a very long list of modules, at which point anyone 
thinking of emulating the behaviour of those modules would promptly give up.

------------------------

(BTW here's a port of that benchmark based on the Lua code:

   https://pastebin.com/raw/ivDaKudX

The actual language is not relevant, as this is clear enough that it 
could probably be re-implemented on anything. The 'files' module is only 
needed for openfile, closefile, and 'outbyte', which should be standard 
in any language. ('writebytes' might not be, so that was changed to a loop.)

The point of all this: writing clean simple code has a big advantage, 
and I think my version is one of the cleanest (even though it writes to 
a file, not the console).

Although it should be pointed out that these programs are pulling out 
all the stops in order to get the best performance; clarity wasn't a 
priority. But they should all use the same algorithm (to be within the 
rules), and it is that we're trying to extract.)

-- 
bartc