Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Mark Lawrence <breamoreboy@yahoo.co.uk>
Newsgroups: comp.lang.python
Subject: Re: The Cost of Dynamism (was Re: Pyhon 2.x or 3.x, which is faster?)
Date: Mon, 21 Mar 2016 03:59:37 +0000
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On 21/03/2016 02:04, BartC wrote:
> On 21/03/2016 01:35, Chris Angelico wrote:
>> On Mon, Mar 21, 2016 at 12:28 PM, Mark Lawrence
>> <breamoreboy@yahoo.co.uk> wrote:
>>> I got to line 22, saw the bare except, and promptly gave up.
>>
>> Oh, keep going, Mark. It gets better.
>>
>> def readstrfile(file):
>>      try:
>>          data=open(file,"r").read()
>>      except:
>>          return 0
>>      return data
>>
>> def start():
>>      psource=readstrfile(infile)
>>      if psource==0:
>>          print ("Can't open file",infile)
>>          exit(0)
>>
>>
>>
>> So, if any exception happens during the reading of the file, it gets
>> squashed, and 0 is returned - which results in a generic message being
>> printed, and the program terminating, with return value 0. Awesome!
>
> I don't have a clue about exceptions, but why wouldn't read errors be
> picked up by the same except: block?

If you don't understand exceptions, you don't understand Python, which 
prefers EAFP than LBYL.  See 
https://docs.python.org/3/glossary.html#term-eafp and 
https://docs.python.org/3/glossary.html#term-lbyl

>
> But I've anyway sprinkled one or two more try/excepts in there and put
> some actual exception codes in. However, this readstrfile() is just
> there to load the file into memory and avoid having a 200,000-line
> string in the program.
>

Just let the exception bubble up if anything goes wrong.  In most 
circumstances that's far better than masking everything that could 
possibly go wrong.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence