Thanks will try.

def __init__(self, title): slug = xxx(title) super().__init__(title=title, slug=slug)

Hmm now I have class Article(db.Entity): _table_ = 'articles' slug = Required(str, 200, unique=True) title = Required(str, 255) description = Required(LongStr) body = Required(LongStr) created_at = Required(datetime, 0, default=datetime.utcnow) updated_at = Required(datetime, 0, default=datetime.utcnow) author = Required(User, reverse="articles") favorited = Set(User, reverse="favorites") comments = Set("Comment") tag_list = Set("Tag") def _unique_check(self, text, uids): if text in uids: return False return not self.exists(slug=text) def _slugify_url_unique(self, text): slugify_url_unique = UniqueSlugify( unique_check=self._unique_check, uids=['feed'] ) slugify_url_unique.to_lower = True slugify_url_unique.stop_words = ('a', 'an', 'the') slugify_url_unique.max_length = 200 return slugify_url_unique(text) def __init__( self, title, description, body, author, tag_list ): slug = self._slugify_url_unique(title) super().__init__( slug=slug, title=title, description=description, body=body, author=author, tag_list=tag_list )But getting AttributeError: 'Article' object has no attribute 'exists'. Shouldn't it have that attribute?

No, this method is defined for entity class only. You can write self.__class__.exists(...) instead. Maybe in the future we'll make it a usual classmethod which can be called both from class and from object

@akozlovsky Why does def before_insert(self): self.slug = self._slugify_url_unique(self.title)doesn't work?

What exception did you get?

ValueError: Attribute Article.slug is required

before_insert works before the INSERT command is sent to the database, not before the __init__ code is executed. When the attribute is specified as required, Pony does not allow to create an instance of object without that attribute defined. We can add something like option delayed_check=True to allow temporary creation of object without all required attributes, but I'm not sure this is a good practice. I think you can create make_article function (or Article.make classmethod) which will create a slug before creating an Article instance: class Article(db.Entity): ... @classmethod def make(cls, **kwargs): if `slug` not in kwargs: kwargs['slug'] = cls._slugify_url_unique(kwargs['title']) return cls(**kwargs) With this approach, you need to make _slugify_url_unique and _unique_check classmethods too

And would it be possible to set a function as default value?

Sure, you can do something like: from datetime import datetime from uuid import UUID, uuid4 class MyObject(db.Entity): created_at = Required(datetime, default=datetime.now) guid = Required(UUID, unique=True, default=uuid4)

But not with an argument, right?

Sure. With argument it will be just one specific value

def __init__(self, title): slug = xxx(title) super().__init__(title=title, slug=slug)

Thanks again! Using __init__() works for me.

I either just use Optional, or set a fake initial value to be overwritten in after_insert

Yeah thought about that. A reason why you use after_insert not before_insert?

oh that was just an example :) depends on the usecase

As slug is unique I think I cannot use Optional. Maybe use UUID as default.

that would work

Just for case it is possible for unique attribute to be Optional, because in all databases except MS SQL Server NULL values are not considered to be unique

So it is possible to have multiple NULL values in unique column

Oh so I could set default to null and make it Optional.

yes

So this sounds actually the least 'hacky'. 😉

@akozlovsky Getting TypeError: Default value for non-nullable attribute Article.slug cannot be set to Nonewhen setting class Article(db.Entity): _table_ = 'articles' slug = Optional(str, 200, unique=True, default=None) title = Required(str, 255)From the documentaion unique optional fields should be nullable: > If an optional string attribute is used as a unique key or as a part of a unique composite key, it will always have nullable set to True automatically.

I'm getting also pony.orm.core.TransactionIntegrityError: Object Article[new:1] cannot be stored in the database. IntegrityError: NOT NULL constraint failed: articles.slugfor SQLITE when not using before_insert. When adding nullable=True and using def before_insert(self): if not self.slug: self.slug = self._slugify_url_unique(self.title)everything works fine! 😃

^^'

Which is the proper way to separate the models into different files? I have users.py with the following content: from pony.orm import * from datetime import datetime db = Database() class User(db.Entity): uuid = PrimaryKey(int, auto=True) name = Required(str) token = Required(str) registered_at = Required(datetime) active = Required(bool) And the main.py with this: from pony.orm import * from models.users import User def main(): db = Database() db.bind(provider='mysql', host='127.0.0.1', port=3306, user='root', passwd='example', db='example') sql_debug(True) db.generate_mapping(create_tables=True) if __name__ == '__main__': main() But when I execute the main function it does not create the tables and it does not throw any exception. The code works if I put it into the same file.

You have to import db from users. Not create it a second time.

Will try tomorrow morning and see if it works. Thank you :D

hi all! Is pony has a on_save or before_save methods for calling on pony entities creation? i want to do some actions before pony save data

hi Nickolai https://docs.ponyorm.com/api_reference.html#entity-hooks

Hey - At work were having a discussion about whether to bind and execute pony calls in functional manner, or, whether to keep the bindings and store them in a dictionary. We're connecting to multiple databases as multiple users, so the diversity cannot be avoided. Any thoughts on performance here? A) Use and drop the bindings - the users wont notice. B) Keep and maintain the bindings? it matters.

Is it in a long running process?

Could be.

Let's say yes.

How many connections?

<100

are all connections used roughly equally?

Yes. They're balanced.

So it seems like no individual connection will ever go a long time without being used?

The user-session lifetime is on average 120 minutes.

So I was thinking of purging them after that.

Unless the databases suffer a shortage of connections, I think keeping around all connections is reasonable

connections are cheap for both the database and python

It's all postgres, so I doubt the database will suffer :-)

Agreed

Thank M.👍

does the postgres driver have automatic timeouts with automatic reconnects?

I wouldn't know. I've just dictated to the devs to use pony.

I believe pony uses psycopg behind the scenes.

Yep, psycopg2

I think it'll be fine

We haven't constrained the timeout settings.

Final question: If the binding is lost either side, do you know if pony tries to rebind/reconnect?

I don't know I'm afraid, you could probably test it by killing postgres, waiting a few minutes then launching postgres again, then try to run a query

"testing determines all truth". I'll do that.

Hi Bjorn! On db.bind(...) Pony opens connection to the database and then store it in a thread-local connection pool. When application code enters db_session and makes a query, Pony takes already opened connection from the pool and use it. After exiting db_session, connection is returned to the pool. If you enable logging, you will see RELEASE CONNECTION message from Pony. It means that the connection is not closed, but was returned to the connection pool. Sometimes connection is closed by database server, for example when database server was restarted. After that a previously opened connection becomes invalid. If such disconnect happens, most probably it was between db_sessions, but sometimes it may happens right during active db_session. Pony is prepared to such situations, and may reconnect to the database in an intelligent matter. If Pony executes a query and receive an error that connection is closed, it check the state of db_session in order to know was any updates already sent to the database during current db_session. If db_session just started, or all queries were just SELECTs, Pony assumes it is safe to re-open connection under the hood and continue the same db_session as if nothing unusual is happened. But if some updates were already sent to the database during active db_session before the previous connection becomes invalid, it means these updates are lost, and it is impossible to continue this db_session. Then Pony throws an exception. But in most cases Pony is able to reconnect silently so application code don't notice anything. If you want to close connection which is stored in the connection pool, you can perform db.disconnect() call. In multi-threaded application this needs to be done in each thread separately

Wow. Thanks. Let me read it twice. ...

Wow x 2. I think we should add this to the docs in https://docs.ponyorm.com/transactions.html#working-with-db-session

under "handling disruptions"

By default pony create db tables with latin1_swedish_ci encoding. I using db.generate_mapping(create_tables=True) snippet. But it this case i cant save unicode strings(python3 strings) for entity type str. What i should to do to resolve this problem?

Wow x 2. I think we should add this to the docs in https://docs.ponyorm.com/transactions.html#working-with-db-session

I agree, we will add this to the docs

By default pony create db tables with latin1_swedish_ci encoding. I using db.generate_mapping(create_tables=True) snippet. But it this case i cant save unicode strings(python3 strings) for entity type str. What i should to do to resolve this problem?

Hmm, this is strange, I think Pony should use UTF8 by default

I think Pony does not specify encoding when creating a table, and use default encoding for the database. When you create a new database, please set UTF8 encoding as default

I think Pony does not specify encoding when creating a table, and use default encoding for the database. When you create a new database, please set UTF8 encoding as default

I cant see anything about creation db( or table) with custom encoding in official documentation. Where it's described?

Pony cannot create a database. Creating database requires admin privileges, and Pony typically connects as a restricted user. It may be dangerous to connect to database from application code using admin privileges. Regarding encoding, previously Pony supported working with custom encoding, but now it assumes the encoding is UTF8. Maybe we can reconsider this

If I create a composite_key(a, b) with postgres, does that imply that an index has also been created on a and b?

ah it seems that postgres creates an index as part of creating the constraint

it was not helping a simple query at all, but an additional index on a made the query fast

my above messages are an example of the risks of doing database performance analysis after only half a cup of coffee.

Hi guys, we released Pony 0.7.3. You can see description here: https://blog.ponyorm.com/2017/10/23/pony-orm-release-0-7-3/

Trying to create some object that have relationships but running into an Attribute is required error

If an attribute is required, you need to assign it durng object initialization. In order to do this, you need to create an object on the other side of relationship earlier, and specify it in constructor arguments of you second object

Hi guys, we released Pony 0.7.3. You can see description here: https://blog.ponyorm.com/2017/10/23/pony-orm-release-0-7-3/

Could you clarify what breaking change there will be in the ORDER BY?

If an attribute is required, you need to assign it durng object initialization. In order to do this, you need to create an object on the other side of relationship earlier, and specify it in constructor arguments of you second object

Let me try

Could you clarify what breaking change there will be in the ORDER BY?

See https://docs.ponyorm.com/api_reference.html#Query.order_by

See https://docs.ponyorm.com/api_reference.html#Query.order_by

It doesn't really says what changed. Only that the other method does what order_by did before

# After the 0.8 release q5 = q.order_by(lambda o: o.customer.name)

@luckydonald So it will be similar to the new where method.

@akozlovsky The @db_session 'ddl' parameter seems not be documented.