Proposal: Inline Import

Bengt Richter bokr at oz.net
Sun Dec 11 09:42:12 CET 2005


On Sat, 10 Dec 2005 19:40:08 -0800, Robert Kern <robert.kern at gmail.com> wrote:

>Bengt Richter wrote:
>
>> Are you willing to type a one-letter prefix to your .re ? E.g.,
>> 
>>  >>> class I(object):
>>  ...     def __getattr__(self, attr):
>>  ...         return __import__(attr)
>
>[snip]
>
>> There are special caveats re imports in threads, but otherwise
>> I don't know of any significant downsides to importing at various
>> points of need in the code. The actual import is only done the first time,
>> so it's effectively just a lookup in sys.modules from there on.
>> Am I missing something?
>
>Packages.
>
Ok, if you're willing to add a trailing '._' to indicate the end of a package path,
and start it with a P instead of an I, you could try the following (just a hack, not tested beyond
what you see, (again ;-) )

----< impexpr.py >--------------------
class I(object):
    __cache = {}
    def __getattr__(self, attr, cache = __cache):
        try: return cache[attr]
        except KeyError:
            cache[attr] = ret = __import__(attr)
            return ret
    getdotted = __getattr__

class P(I):
    def __init__(self):
        self.elems = []
    def __getattr__(self, attr):
        if attr == '_':
            dotted = '.'.join(self.elems)
            mod = self.getdotted(dotted)
            for attr in self.elems[1:]:
                mod = getattr(mod, attr)
            self.elems = []
            return mod
        else:
            self.elems.append(attr)
            return self

P, I = P(), I()
--------------------------------------

 >>> from ut.impexpr import I, P
 >>> I.math.pi
 3.1415926535897931
 >>> I.os.path.isfile
 <function isfile at 0x02EB5534>
 >>> P.ut.miscutil._.prb
 <function prb at 0x02F1EBC4>
 >>> type(I)._I__cache.keys()
 ['ut.miscutil', 'os', 'math']
 >>> P.ut.miscutil._.disex
 <function disex at 0x02F1EDBC>
 >>> type(I)._I__cache.keys()
 ['ut.miscutil', 'os', 'math']

 >>> I.ut.miscutil
 <module 'ut.miscutil' from 'c:\pywk\ut\miscutil.pyc'>
 >>> I.ut
 <module 'ut' from 'c:\pywk\ut\__init__.pyc'>

I am not recommending this particularly. I just like to see how close
python already is to allowing the spelling folks initially think requires
a language change ;-)

Regards,
Bengt Richter



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