Understanding Python's interpreter

[Steve Holden]

Rafael Almeida wrote:
> On Sat, 07 Apr 2007 04:35:49 +0200
> Gabriel Genellina <gagsl-py2 at yahoo.com.ar> wrote:
> 
>> Speed? Eficiency? File size? Ease of use?
>> A .pyc *could* be written in ASCII, but what do you gain? Replacing a 
>> few trivial functions in the Python core with a printf/scanf equivalent? 
>>   At the same time you lose a lot of speed, so I don't see the point.
> 
> Hm, I didn't realise that it would be that much slower.

You may mistakenly believe that casts are an expensive operation, when 
in fact they take no time at all - they merely instruct the compiler to 
treat specific pieces of data in specific ways.

> 
>> Why harder? Once you read the file, they're just numbers. Anyway, being 
>> harder to program the *interpreter* is not a problem, if you gain 
>> something like speed or eficiency for the interpreted language.
> 
> Well, it's harder to get 4 bytes and create an int out of it in a
> portable way than just call strtol or scanf, that's what I thought
> while I was coding my interpreter. It's not the hardest thing to do,
> of course, but it made me wonder why not just do the simplest thing.
> 
Because they aer smarter than you, without wishing to be too rude.

> Since I've never seen a .pyc bigger than a few kilobytes, I thought an
> ascii file would take more space, but it wouldn't be anything really
> prohibitive.
> 
> I didn't think using strtol would make that much difference in speed.
> But now you talked about it, and after thinking a little bit more about
> it, I'm convinced that the speed difference may be relevant.
> 
Which is a good reason to think about things *before* you post.

>>> And when I tried to code an assembler my problems got greater, as I
>>> wanted to code it in python (the interpreter was in C++) and I had a
>>> hard time trying to figure out how I would print something that's not a
>>> ascii or unicode string. As for the benefits, I couldn't figure out any.
>> Sorry, I could not understand what you said here.
> 
> It's not anything important, I was just saying that I had to write a
> little more code to make an integer such as 0xff into '\0\0\0\377' than
> it would need to just print the integer. Well, unless there's already a
> python function that does just that and I didn't know about. It's was
> just an example on how writting in ascii is easier.

Speed, baby, speed.

regards
  Steve
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