[Python-ideas] shlex escapes without Posix mode

[Andrew Barnert]

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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