Why did Quora choose Python for its development?

[Daniel Kluev]

On Mon, May 23, 2011 at 5:06 PM, Octavian Rasnita <orasnita at gmail.com> wrote:
> There are more, but a single eloquent feature is the possibility of
> interpreting variables in strings which cannot be done so nice in Python.

I've should probably mentioned it earlier, but I'm not Perl expert,
not following its development and can't be bothered to read its docs.
Could you please provide examples of features you mention with
expected result, so I could suggest reasonable Python analogue?

> This is false. Explicit in this case means to write code in 2 places for
> doing a certain thing, and maintaining means changing the code in 2 places,
> which is harder and prone to errors.

Not sure what do you mean by 'write code in 2 places'. All mapping
code is located in routes config, including all needed args
validation.
But if you want to couple it with controller code, there, as I said,
are numerous ways to do it. You can even do something like this:

class SomeController(BaseController):
    ...
    @map(conditions=dict(method='GET'))
    def some_method(self, arg1:int, arg2:str):
         ...

so it would be called via /somecontroller/some-method/1/blabla with
trivial decorator.

> (unless in Pylons/Pyramid can be also defined chained mappings and mappings
> based on regular expressions).

Not sure what do you mean by "based on regular expressions". Routes
paths ARE regular expressions. Conditions are regexes too.

As for chained mappings - no idea, never had the need in such thing.

> Yes, the single difference is that Catalyst supports all of them, and it
> also supports using any templating system, and any ORM and any form
> processor, while some of the Python web frameworks don't support absolutely
> everything and you need to abandon some preferred modules for beeing able to
> use some other modules which are supported.

Pyramid and Pylons let you use pretty much any templating package and
ORM as well. There is nothing in them that would block such modules.

> I've checked the documentation for some of them and I've seen that most of
> them don't support sub-selects and some of them require using plain SQL code
> in their construct for more complex queries.
> Please tell me which of them supports sub-selects, and are able to return
> objects for date and datetime fields that have methods for beeing able to
> print just the year or day, or the months names in the specified locale
> because it would be useful.

Python has builtin type for DateTime, and SQLAlchemy, for example,
returns exactly that:

#> python
Python 2.7.1 (r271:86832, May 17 2011, 19:31:41)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from sadt import Test, Session
>>> import datetime
>>> Test(1)
<Test(1, 1, 2011-05-23 18:53:39.459054)>
>>> Test(2)
<Test(2, 2, 2011-05-23 18:53:51.859754)>
>>> t1 = Session.query(Test).filter(Test.val == 1).one()
>>> t1
<Test(1, 1, 2011-05-23 18:53:39.459054)>
>>> t1.date
datetime.datetime(2011, 5, 23, 18, 53, 39, 459054)
>>> t1.date.year
2011
>>> t1.date.month
5
>>> print Session.query(Test).filter(Test.date == datetime.datetime(2011, 5, 23, 18, 53, 39, 459054)).one()
<Test(1, 1, 2011-05-23 18:53:39.459054)>
>>> print Session.query(Test).filter(Test.date > datetime.date(2010, 1, 1)).all()
[<Test(1, 1, 2011-05-23 18:53:39.459054)>, <Test(2, 2, 2011-05-23
18:53:51.859754)>]

sadt sources here if interesting: http://pastebin.ca/2067372

So as you see, datetime is not only returned properly, but you can
also do queries with either date or datetime values, including
comparison and range.

Subqueries are fully supported too:
>>> ...
>>> Session.query(Test).from_self().all()
2011-05-23 19:07:02,662 INFO sqlalchemy.engine.base.Engine.0x...552c
SELECT anon_1.test_id AS anon_1_test_id, anon_1.test_val AS
anon_1_test_val, anon_1.test_date AS anon_1_test_date
FROM (SELECT test.id AS test_id, test.val AS test_val, test.date AS test_date
FROM test) AS anon_1
2011-05-23 19:07:02,662 INFO sqlalchemy.engine.base.Engine.0x...552c ()
[<Test(1, 1, 2011-05-23 19:06:36.804128)>, <Test(2, 1, 2011-05-23
19:06:36.808022)>, <Test(3, 1, 2011-05-23 19:06:36.810698)>, <Test(4,
2, 2011-05-23 19:06:36.813357)>, <Test(5, 3, 2011-05-23
19:06:36.816373)>]

This is most trivial example of subqueries, since I'm too lazy to
produce proper tables to demonstrate it, but SQLAlchemy has very good
subquery support, as its typical way to deal with one-to-many
relations (but it does support other loading strategies as well,
including inner/outer joins or lazy loading).

> it can do but DBIx::Class cannot, because otherwise it would be very simple
> for anyone to just say "go to read the documentation and see how great it
> is".

But "go to read the docs" argument works both ways - I have zero
knowledge of DBIx::Class, so obviously I cannot say what features it
lacks compared to SQLA.
However this is what I wanted to highlight - you cannot simply state
that "Perl offers more advanced modules and libraries which are not
available for Python" if you don't have reasonable experience with
according Python modules.


-- 
With best regards,
Daniel Kluev