[Python-ideas] shlex escapes without Posix mode

[Ryan]

ksh has parenthesis and shell functions. Still a shell language.

And shell languages pretty much always have escapes.

Andrew Barnert <abarnert at yahoo.com> wrote:

>Are you trying to use shlex to parse code for some language other than
>sh or another shell language? It's not meant to be useful for perl or C
>or whatever.
>
>A general-purpose quoting, escaping, splitting, and joining module that
>could be configured to handle everything from sh to C to CSV could be
>cool, but shlex isn't it.
>
>On Jul 26, 2013, at 18:43, Ryan <rymg19 at gmail.com> wrote:
>
>> The main thing is that this:
>> 
>> ("d")
>> 
>> In Posix mode gets split into this:
>> 
>> (d)
>> 
>> But, say the language has callable functions. I'd have to
>re-shlex.split the line to split the arguments. And, even then, the
>quotes already got destroyed.
>> 
>> Escapes, however, are useful in practically every language.
>Restricting them to POSIX mode just kills it. And I had tried to see if
>I could implement it myself, but reading source code on Android SL4A is
>absolutely painful. And, whenever I pull up a computer, I always have a
>goal in mind and haven't got a chance to tweak it.
>> 
>> I've never quite come across a language without some form of escapes.
>And, I can't think of an occasion where I'd use POSIX mode. Therefore,
>in the end, it would end up being better if you could enable the
>escapes individually. POSIX mode would have priority over the escape
>option. The instance could.be created like this:
>> 
>> lex = shlex.shlex(escape='\\')
>> 
>> The default value would be None. That would change the value of
>pex.escape to '\\'. If the value is None, escapes are disabled.
>> 
>> Steven D'Aprano <steve at pearwood.info> wrote:
>>> 
>>> Hi Ryan, and welcome.
>>> 
>>> 
>>> On 26/07/13 05:22, Ryan wrote:
>>>> Note: This is my first post to the mailing list, so I'm not sure if
>I'm doing something wrong or something.
>>>> 
>>>> I've been playing around with shlex.lately, and I mostly like it,
>but I have an idea.
>>>> 
>>>> Have an option with the ability to enable certain Posix mode
>features selectively, most particularly character escapes. It could be
>something like, if Posix mode is disabled, the string of escape
>characters is set to empty or None, and assigning a value to it enables
>that feature in non-Posix mode.
>>> 
>>> 
>>> That's a good start, but it's awfully vague. "Something like"?
>Concrete ideas will help. Actual working code is best (although be
>cautious about posting large
>>> amounts of code here -- a few lines is fine, pages of code, not so
>much), or at least pseudo-code demonstrating how and when somebody
>might use this proposed feature.
>>> 
>>> Good use-cases for why you might want the feature also helps. Under
>what circumstances would you say "Well, I don't want POSIX mode, but I
>do want POSIX escape sequences"?
>>> 
>>> Ultimately, don't be surprised or disappointed at negative
>reactions. Negative reactions are better than silence -- at least it
>means that people have read, and care enough to comment, on your post,
>while silence may mean that nobody cares, or simply don't understand
>what you're talking about and are too polite to say so.
>>> 
>>> We tend to be rather conservative about adding new features.
>Sometimes it takes *years* for features to be added, or they are never
>added, if nobody who cares about the feature steps up to program it.
>Remember too that new code has to carry its weight: code not only has
>one-off costs (code doesn't
>>> write itself, neither does the documentation), but also on-going
>costs (maintenance, bug-fixes, new features for users to learn, etc.),
>and no matter how low that cost is, it is never zero, so if the benefit
>from that feature is not more than the cost, it will probably be
>rejected.
>>> 
>>> Two good posts you should read, by one of the senior core
>developers, are:
>>> 
>>>
>http://www.boredomandlaziness.org/2011/04/musings-on-culture-of-python-dev.html
>>> 
>>>
>http://www.boredomandlaziness.org/2011/02/status-quo-wins-stalemate.html
>>> 
>>> 
>>> If you take nothing else from my reply, at least take from it these
>two questions:
>>> 
>>> "Under what circumstances would this feature be useful to you? And
>would they be useful enough that you personally would program this
>feature, if you had the
>>> skills?"
>> 
>> -- 
>> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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