Friday Filosofical Finking: Import protections

DL Neil PythonList at DancesWithMice.info
Thu Apr 18 00:36:53 EDT 2019


On 18/04/19 1:24 PM, Cameron Simpson wrote:
> On 17Apr2019 21:45, MRAB <python at mrabarnett.plus.com> wrote:
>> On 2019-04-17 21:20, DL Neil wrote:
>>> Do you bother with exception handling for import statements?
> [...]
>> Catch only what you (well, the script) can fix.
>>
>> If it needs numpy, but can't import numpy, then when can it do? Might 
>> as well just let it fail.
> 
> I'm of this mind too, but...
> 
>> I suppose an alternative might be to try to download and install numpy 
>> and then retry, but what if it can't be downloaded, or the 
>> installation fails?
> 
> As an example of what an open ended can of worms attempts recovery might 
> be, yeah. How hard do you try? But also, "installation fails": that 
> isn't always a clean situation: it can litter the install area with 
> partial junk.
> 
> But this is also a bad example: it is something an _invoked_ programme 
> should never try to do. Except by specific deliberate design and 
> request, a running application shouldn't presume it has rights to 
> install additional things, or even to try. I have personally (though 
> metaphorically) clipped devs across the ear for doing themselves the 
> moral equivalent of the above: try thing, then just "sudo try thing" 
> when it was forbidden.
...

+1


> Installing additional packages is the same as self modifying code: as a 
> rule, the admins install packages, not the app.

+1


> Sorry, ranting now over.

Not at all, an excellent point which needs to be taken out and 
dusted-off, every now-and-again - particularly for such ear-clipping 
training exercises!

-- 
Regards =dn


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