[Python-ideas] Proposal: Query language extension to Python (PythonQL)

Sun Mar 26 07:10:54 EDT 2017

Hi Michel!

> On 25 Mar 2017, at 22:43, Michel Desmoulin <desmoulinmichel at gmail.com> wrote:
> 
> Hello,
> 
> I've been following PythonQL with interest. I like the clever hack using
> Python encoding. It's definitely not something I would recommend to do
> for an inclusion in Python as it hijack the Python encoding method,
> which prevent your from... well choosing an encoding. And requires to
> have a file.

This was done as a temporary hack, we definitely want to move away from this at some point.

> 
> However, I find the idea great for the demonstration purpose. Like LINQ,
> the strength of your tool is the integrated syntax. I myself found it
> annoying to import itertools all the time. I eventually wrote a wrapper
> so I could use slicing on generators, callable in slicing, etc for this
> very reason.
> 
> However, I have good news.
> 
> When the debate about f-strings was on this list, the concept has been
> spitted in several parts. The f-string currently implemented in Python
> 3.6, and an more advanced type of string interpolation: the i-string
> from PEP 501 (https://www.python.org/dev/peps/pep-0501/) that is still
> to be implemented.
> 
> The idea of the i-string was to allow something like this:
> 
> mycommand = sh(i"cat {filename}")
> myquery = sql(i"SELECT {column} FROM {table};")
> myresponse = html(i"<html><body>{response.body}</body></html>")
> 
> Which would then pass an object to sql/sh/html() with the string, the
> placeholders and the variable context then allow it to do whatever you
> want. Evaluation of the i-string would of course be lazy.
> 
> So while I don't thing PythonQL can be integrated in Python the way it
> is, you may want to champion PEP 501. This way you will be able to
> provide a PQL hook allowing you to do something like:
> 
> pql(i"""select (x, sum_y)
>           for x in range(1,8),
>               y in {stuff}
>           where x % 2 == 0 and y % 2 != 0 and x > y
>           group by x
>           let sum_y = sum(y)
>           where sum_y % 2 != 0
> """)
> 
> Granted, this is not as elegant as your DSL, but that would make it
> easier to adopt anywhere: repl, ipython notebook, files in Python with a
> different encoding, embeded Python, alternative Python implementations
> compiled Python, etc.
> 
> Plus the sooner we start with i-string, the sooner editors will
> implement syntax highlighting for the popular dialects.
> 
> This would allow you to spread the popularity of your tool and maybe
> change the way it's seen on this list.

Hmm, I don’t quite understand what’s the difference here with regular string and
executing them, i.e. I think we can do this right now without i-strings.

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