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Date: Wed, 26 Nov 2014 00:04:15 -0600
From: Tim Daneliuk <tundra@tundraware.com>
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To: Ben Finney <ben+python@benfinney.id.au>, python-list@python.org
Subject: Re: Quotation Ugliness
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On 11/25/2014 07:54 PM, Ben Finney wrote:
> Tim Daneliuk <tundra@tundraware.com> writes:
>
>> Here's the problem: Determine is the string S appears *outside* or
>> *inside* any such quotation.
>
> This is a problem for parsing text. There is no general, simple
> solution.
>
> If someone tries to convince you they have one, be highly suspicious: it
> will either be not general, or not simple, or neither simple nor general.
>
>> I know lots of ugly/complicated/heavyweight ways to solve this, but
>> I'm wondering if any of you geniuses have a pythonic/elegant/short
>> algo that solves this.
>
> I would recommend one of the following, in descending order of
> preference:
>
> * Try very hard to change the requirements so that the input must be in
>    a mature well-known format for which there are *existing*, maintained,
>    reliable parsers. Use those instead of rolling your own.
>
> * If that fails, then: Try very hard to drastically simplify the
>    specified input format so that every possible input is either
>    obviously invalid, or obviously has exactly one meaning.
>
> * If that fails, then: Bite the bullet and acknowledge you will be
>    entering the complexities of parsing text. Use a mature library for
>    writing your parser; don't attempt to write a parsing library
>    yourself. *This is the worst option*; changing the requirements for
>    input will be much less pain than this.
>

In this case, I am not trying to write a fullblown language or recover
from syntax errors.   Here's a usecase - I want to know whether I need
to use a sudo password when the user passes a command on the command line
of a program:

someprog.py uname && sudo cat /etc/sudoers

vs.

someprog.py uname && echo "sudo cat /etc/suoders"


In the first instance, I need the sudo passoword, in the second I don't.



-- 
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Tim Daneliuk     tundra@tundraware.com
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