Life's better without builtins? (was: Life's better without braces)

[Niels Diepeveen]

Gerrit Holl schreef:
> 
> <quote name="Andrew M. Kuchling" date="951150482">
> > [2] I occasionally think about this problem.  The setup: GvR was far
> > too profligate in adding functions to bltinmodule.c that could have
> > been written in pure Python instead.  So, how many built-in functions
> > can you re-implement in pure Python?
> 
> These are possible:
> 
> abs, callable, chr, delattr, divmod,
> execfile, filter, getattr, hex, input, int, isinstance, issubclass,
> len, list, long, map, max, min, oct, range, raw_input, reduce, reload,
> repr, setattr, tuple, vars.

Do you have some source code of this? I can't think of a way to do
reload() or tuple().

> 
> These aren't:
> 
> apply, buffer, coerce, compile, complex, dir, eval, exit, globals, hash,
> id, intern, locals, round, slice, type, xrange

I think you're a bit pessimistic there. For example:

_interns = {}

def intern(s):
    try:
        return _interns[s]
    except KeyError:
        _interns[s] = s
        return s
        
class _slice_hack_class:
    def __getitem__(self, n):
        return n
        
_slice_hack = _slice_hack_class()
        
def slice(*args):
    if len(args) == 0:
        raise TypeError('slice requires at least 1 argument; 0 given')
    elif len(args) == 1:
        return _slice_hack[:args[0]:]
    elif len(args) == 2:
        return _slice_hack[args[0]:args[1]:]
    elif len(args) == 3:
        return _slice_hack[args[0]:args[1]:args[2]]
    else:
        raise TypeError('slice requires at most 3 arguments; ' +
`len(args)` + ' given')

def round(val, prec = 0):
    if val >= 0.0:
        return 10.0 ** (-prec) * float(long(val * 10.0 ** prec + 0.5))
    else:
        return 10.0 ** (-prec) * float(long(val * 10.0 ** prec - 0.5))


-- 
Niels Diepeveen
Endea automatisering