Re: mapping objects
Thanks for the response Cameron. No amount of 'googling' could provide me with that caliber response :-) So, it seems regardless I would need a database. On Sun, Feb 2, 2014 at 1:58 AM, Cameron Simpson c...@zip.com.au wrote: On 01Feb2014 20:46, Rita rmorgan...@gmail.com wrote: I want to learn more about ORMs so I stumbled upon, SqlAlchemy. If i had a JSON document (or XML, CSV, etc.._) is it possible to convert it to a SQLAlchemy objects? I like the ability to query/filter ( http://docs.sqlalchemy.org/en/rel_0_9/orm/tutorial.html#common-filter-operators ) the data assuming I set up the proper schema. Well, not as directly as you might hope. As I recall, SQLAlchemy ORMs provide an easy way to make objects representing database entities and whose methods automatically drive the necessary SQL actions to manipulate them. On that basis, you won't get anywhere without loading up the JSON/XML/etc, parsing it for relevant information (trivial with CSV, less so for structured data like JSON or XML), and storing it in a database. To which you then point SQLAlchemy. So you're already doing the fiddly bit just to get stuff into the database. The neat filter operations you cite are actually done by special methods on the objects representing tables and columns. For example, User.name == None is done via the __eq__ method of User.name. And they return strings: bare SQL. The beauty of this is that one can write almost idiomatic python, and SQLA will generate correct SQL in the right dialect for the database backend, and with all the values correctly escaped. However, it does presume you _already_ have a backend that can be queried with SQL. Also, is this a valid way to use an ORM suite? Well, in principle sure. But SQLA won't do it for you directly. It really is for data already stored in an SQL queriable database. Your point about using SQLA's filter operations is right, _provided_ you have already loaded the original data into a database with the right schema. If you've done that work, then SQLA may well serve you well from that point on. Cheers, -- Cameron Simpson c...@zip.com.au We knew Army cadets were involved because they cut through two fences to get to the goats, and 15 feet away there was an unlocked gate. - a director of sports information in the Navy, regarding the theft of some mascots from the Naval Academy by Army rivals -- https://mail.python.org/mailman/listinfo/python-list -- --- Get your facts first, then you can distort them as you please.-- -- https://mail.python.org/mailman/listinfo/python-list
Re: mapping objects
On 02Feb2014 07:41, Rita rmorgan...@gmail.com wrote: Thanks for the response Cameron. No amount of 'googling' could provide me with that caliber response :-) So, it seems regardless I would need a database. To use SQLA, yes. The SQLite backend is a very cheap/easy way to start; local files, no server needed etc. In unit tests I use this DB URL: 'sqlite:///:memory:'. It makes an in-memory database. Of course, it vanishes as soon the the program exits, but for this purpose that's fine. BTW, if you're parsing XML data specificly, look at BeautifulSoup 4 and XPath (search syntax; IIRC the XML objects you get from BS4 can use it to locate things). Cheers, -- Cameron Simpson c...@zip.com.au The nice thing about standards is that you have so many to choose from; furthermore, if you do not like any of them, you can just wait for next year's model. - Andrew S. Tanenbaum -- https://mail.python.org/mailman/listinfo/python-list
mapping objects
Hello, I want to learn more about ORMs so I stumbled upon, SqlAlchemy. If i had a JSON document (or XML, CSV, etc.._) is it possible to convert it to a SQLAlchemy objects? I like the ability to query/filter ( http://docs.sqlalchemy.org/en/rel_0_9/orm/tutorial.html#common-filter-operators) the data assuming I set up the proper schema. Also, is this a valid way to use an ORM suite? -- --- Get your facts first, then you can distort them as you please.-- -- https://mail.python.org/mailman/listinfo/python-list
Re: mapping objects
On 01Feb2014 20:46, Rita rmorgan...@gmail.com wrote: I want to learn more about ORMs so I stumbled upon, SqlAlchemy. If i had a JSON document (or XML, CSV, etc.._) is it possible to convert it to a SQLAlchemy objects? I like the ability to query/filter ( http://docs.sqlalchemy.org/en/rel_0_9/orm/tutorial.html#common-filter-operators) the data assuming I set up the proper schema. Well, not as directly as you might hope. As I recall, SQLAlchemy ORMs provide an easy way to make objects representing database entities and whose methods automatically drive the necessary SQL actions to manipulate them. On that basis, you won't get anywhere without loading up the JSON/XML/etc, parsing it for relevant information (trivial with CSV, less so for structured data like JSON or XML), and storing it in a database. To which you then point SQLAlchemy. So you're already doing the fiddly bit just to get stuff into the database. The neat filter operations you cite are actually done by special methods on the objects representing tables and columns. For example, User.name == None is done via the __eq__ method of User.name. And they return strings: bare SQL. The beauty of this is that one can write almost idiomatic python, and SQLA will generate correct SQL in the right dialect for the database backend, and with all the values correctly escaped. However, it does presume you _already_ have a backend that can be queried with SQL. Also, is this a valid way to use an ORM suite? Well, in principle sure. But SQLA won't do it for you directly. It really is for data already stored in an SQL queriable database. Your point about using SQLA's filter operations is right, _provided_ you have already loaded the original data into a database with the right schema. If you've done that work, then SQLA may well serve you well from that point on. Cheers, -- Cameron Simpson c...@zip.com.au We knew Army cadets were involved because they cut through two fences to get to the goats, and 15 feet away there was an unlocked gate. - a director of sports information in the Navy, regarding the theft of some mascots from the Naval Academy by Army rivals -- https://mail.python.org/mailman/listinfo/python-list
