C-style static variables in Python?

Stephen Hansen apt.shansen at gmail.invalid
Sat Apr 3 05:11:21 CEST 2010


On 2010-04-02 19:42:29 -0700, Ethan Furman said:

> Terry Reedy wrote:
>>> In<Xns9D4EC021DC8EAduncanbooth at 127.0.0.1>  Duncan 
>>> Booth<duncan.booth at invalid.invalid>  writes:
>>> 
>>>> class Spam(object):
>>>> mongo = None
>>>> def __call__(self, x, y, z):
>>>> if self.mongo is None:
>>>> self.mongo = heavy_lifting_at_runtime()
>>>> return frobnicate(x, y, z, self.mongo)
>> 
>> 
>> Unless one wants the intialization of mongo delayed in case spam is 
>> never called, it can go in __init__ instead.
> 
> As a matter of fact, I have an object that is usually not called during 
> it's modules use, so I put in __getattr__.  Sped the modules load time 
> back up to pert near instantaneous.  :)
> 
> ~Ethan~

I prefer:

class Spam(object):
    def __init__(self):
        self._mondo = None

    def _get_mondo(self):
        if self._mondo is None:
            self._mondo = heavy_lifting_at_runtime()
        return self._mondo

    mondo = property(_get_mondo)

    def __call__(self, x, y, z):
        return frobnicate(x,y,z, self.mondo)

I don't know if properties are really faster or slower then a 
__getattr__, but I find them a lot cleaner if I want to delay some 
calculation until needed like that.

-- 
--S

... p.s: change the ".invalid" to ".com" in email address to reply privately.




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