PEP 378: Format Specifier for Thousands Separator

[Carlos Nepomuceno]

----------------------------------------
> From: kwpolska at gmail.com
> Date: Tue, 21 May 2013 21:06:11 +0200
> Subject: Re: PEP 378: Format Specifier for Thousands Separator
> To: carlosnepomuceno at outlook.com
> CC: python-list at python.org
>
> On Tue, May 21, 2013 at 8:49 PM, Carlos Nepomuceno
> <carlosnepomuceno at outlook.com> wrote:
>> Thank you, but let me rephrase it. I'm already using str.format() but I'd like to use '%' (BINARY_MODULO) operator instead.
>
> There is no real reason to do this. `str.format()` is the new shiny
> thing you should be using all the time. Also, '%' is BINARY_MODULO
> (where did you even get that name from?) if and only if you have two
> numbers, and it performs the modulo division (eg. 27 % 5 = 2)

I did:

>>> def fmt(s):
...     return '%s' % s
...
>>> import dis
>>> dis.dis(fmt)
  2           0 LOAD_CONST               1 ('%s')
              3 LOAD_FAST                0 (s)
              6 BINARY_MODULO
              7 RETURN_VALUE
>>>

Then I've looked for 'BINARY_MODULO' in "Python/ceval.c" and found:

        case BINARY_MODULO:
            w = POP();
            v = TOP();
            if (PyString_CheckExact(v))
                x = PyString_Format(v, w);
            else
                x = PyNumber_Remainder(v, w);


Then I've looked for 'PyString_Format' and found it in "Objects/stringobject.c"

Analysing the code of "stringobject.c" I've found formatint() and formatlong().

I'm not using str.format() because it's slower than '%' and because I love '%'. str.format() looks like Java shit to me!

>> So, the question is: Where would I change the CPython 2.7.5 source code to enable '%' (BINARY_MODULO) to format using the thousands separator like str.format() does, such as:
>>
>>>>>sys.stderr.write('%,d\n' % 1234567)
>> 1,234,567
>
> This will make your code unportable and useless, depending on one
> patch you made. Please don’t do that. Instead,

I'm just learning how to improve things! ;)

>>>>> sys.stdout.write('Number = %s\n' % '{:,.0f}'.format(x))
>> Number = 12,345
>>
>> 'x' is unsigned integer so it's like using a sledgehammer to crack a nut!
>
> In Python? Tough luck, every int is signed. And it isn’t just a
> sledgehammer, it’s something worse. Just do that:
>
>>>> sys.stdout.write('Number = {:,.0f}\n'.format(x))
>
> Much more peaceful.

Indeed! I just cut and pasted my code to create an example for the message. The actual format operation isn't done at the sys.stdout.write().

> You can also do a print, like everyone sane would. Where did you
> learn Python from? “Python Worst Practice for Dummies”?

lol I'm learning from my big mistakes up to now and a ton of online tutorials, besides "Dive into Python" (2004)[1], "Python Programming" (2012)[2] and "Programming Python, 3rd Ed" (2006) [print]

print isn't thread safe. That's why I've chosen sys.stdout.write() -- it's faster and thread safe by default.

I don't need any fancy formating, just need to send the string to screen.


[1] http://www.diveintopython.net/
[1] http://en.wikibooks.org/wiki/Python_Programming

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