hi there hope yu will be able to help me.
im trying to add a post to a blog, now im trying to fetch the name of the user so it
will be diplayed on the site.
def add_new_post():
form = CreatePostForm()
if request.method == 'POST':
user_data = User.query.filter_by(id=current_user.id).first()
user_name_to_post = str(user_data.name)
print(current_user.name)
new_post = BlogPost(
title=form.title.data,
subtitle=form.subtitle.data,
body=form.body.data,
img_url=form.img_url.data,
author=current_user, <-------------------
date=date.today().strftime("%B %d, %Y")
)
db.session.add(new_post)
db.session.commit()
return redirect(url_for("get_all_posts"))
return render_template("make-post.html", form=form, is_active=current_user.is_active)
now as long the author=current_user, it works but it displays "user1"
as the author name on the site.
if im trying to put the name it raise an exaption
new_post = BlogPost(
title=form.title.data,
subtitle=form.subtitle.data,
body=form.body.data,
img_url=form.img_url.data,
author=current_user.name, <------------------
date=date.today().strftime("%B %d, %Y")
AttributeError: 'str' object has no attribute '_sa_instance_state'
i have tried to go more direct into the user and did this idea that i read somewhere.
new_post = BlogPost(
title=form.title.data,
subtitle=form.subtitle.data,
body=form.body.data,
img_url=form.img_url.data,
author=User(name=current_user.name), <--------------
date=date.today().strftime("%B %d, %Y")
)
it gives me this error:
sqlalchemy.exc.IntegrityError: (sqlite3.IntegrityError) NOT NULL constraint failed:
users.email
[SQL: INSERT INTO users (name, email, password) VALUES (?, ?, ?)]
[parameters: ('jay ber', None, None)]
(Background on this error at: http://sqlalche.me/e/13/gkpj)
Traceback (most recent call last)
my databse looks like that:
class BlogPost(db.Model):
__tablename__ = "blog_posts"
id = db.Column(db.Integer, primary_key=True)
author = db.Column(db.String(250), nullable=False)
title = db.Column(db.String(250), unique=True, nullable=False)
subtitle = db.Column(db.String(250), nullable=False)
date = db.Column(db.String(250), nullable=False)
body = db.Column(db.Text, nullable=False)
img_url = db.Column(db.String(250), nullable=False)
author_id = db.Column(db.Integer, db.ForeignKey("users.id"))
author = relationship("User", back_populates="posts")
class User(UserMixin, db.Model):
__tablename__ = 'users'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(50), nullable=False)
email = db.Column(db.String(100), nullable=False)
password = db.Column(db.String(250), nullable=False)
posts = relationship("BlogPost", back_populates="author")
i hope some one can help me with it.
all i want is to display the name of the author as part of the blog post
Related
I have two model classes:
class Programs(db.Model):
__tablename__ = "programs"
id = db.Column(db.Integer, primary_key=True)
title = db.Column(db.String(100), nullable=False)
description = db.Column(db.String(100), nullable=False)
duration = db.Column(db.Integer, nullable=False)
date_created = db.Column(db.DATE, default=datetime.now())
created_by = db.Column(db.String(100))
program_sessions = db.relationship('Program_Session',backref='programs')
class Program_Session(db.Model):
__tablename__ = "program_session"
id = db.Column(db.Integer, primary_key=True)
session_title = db.Column(db.String(100), nullable=False)
session_description = db.Column(db.String(100))
session_year = db.Column(db.Integer)
program_id = db.Column(db.Integer, db.ForeignKey("programs.id"), nullable=False)
students = db.relationship('Student_Registration', backref='program_session')
date_created = db.Column(db.DATE, default=datetime.now())
created_by = db.Column(db.String(100))
I create an object of Programs with:
program = Programs.query.first()
Now I can access all the Program_Sessions from the selected Program:
print(pro.program_sessions)
Is it possible to subquery/query to retrieve only those Program_session in Program whose year is 2021?
Option-1: filter on 'python' (in memory)
Once you get all Program_Sessions (all_sessions = pro.program_sessions), you filter them by sessions_2021 = [item for item in all_sessions if item.session_year == 2021].
Needless to say, this is not efficient at all as lots of data will be loaded from the database to be immediately discarded.
Option2: use Dynamic Relationship Loaders
Define the relationship with lazy="dynamic", which will return a Query and hence you will be able to apply additional criteria to the query:
class Programs(db.Model):
# ...
program_sessions = db.relationship('Program_Session', backref='programs', lazy="dynamic")
program = Programs.query.first()
sessions_2021 = program.program_sessions.filter(Program_Session.year == 2021).all()
Option3: use orm.with_parent [BEST]
sessions_2021 = select(Program_Session).where(with_parent(program, Program_Session.programs)).where(Program_Session.year == 2021)
The answer is yes...
van's answer shows you options for playing with sqlalchemy's query mechanism. But what if you want to write this logic on the Programs class itself? That way anywhere you have a Programs object, you can access the filter.
You can do it in pretty plain python by altering the Programs class like so:
class Programs(db.Model):
__tablename__ = "programs"
id = db.Column(db.Integer, primary_key=True)
title = db.Column(db.String(100), nullable=False)
description = db.Column(db.String(100), nullable=False)
duration = db.Column(db.Integer, nullable=False)
date_created = db.Column(db.DATE, default=datetime.now())
created_by = db.Column(db.String(100))
program_sessions = db.relationship('Program_Session',backref='programs')
'''Here I add a filter that returns only the sessions for a particular year
'''
def program_sessions_by_year(self, year):
return filter(lambda ps: ps.session_year == year, self.program_sessions)
If you care about efficiency, you can get the database to do the filtering for you using a bit more sqlalchemy magic:
from sqlalchemy.orm import object_session
class Programs(db.Model):
__tablename__ = "programs"
id = db.Column(db.Integer, primary_key=True)
title = db.Column(db.String(100), nullable=False)
description = db.Column(db.String(100), nullable=False)
duration = db.Column(db.Integer, nullable=False)
date_created = db.Column(db.DATE, default=datetime.now())
created_by = db.Column(db.String(100))
program_sessions = db.relationship('Program_Session',backref='programs')
'''Improve efficiency by using DB's SQL engine to filter the object.
'''
def program_sessions_by_year(self, year):
return object_session(self)\
.query(Program_Session)\
.filter_by(session_year=year, program_id=self.id)\
.all()
Either way you can then write (where-ever you have a Program object):
# lets say you just want the first program
first_program = Programs.query.first()
# to get the program sessions by year 2021
first_program.program_sessions_by_year(2021)
There's probably a bunch of other ways you could do something like this. SqlAlchemy is a big library. For more background on my answer, have a look at the SQL expressions as Mapped Attributes docs.
I have this schema:
class Company(db.Model):
__tablename__ = 'companies'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(250), nullable=True, default=None)
domain = db.Column(db.String(250), nullable=True, default=None)
organization_id = db.Column(db.Integer, db.ForeignKey('organizations.id'), nullable=False)
class Contact(db.Model):
__tablename__ = 'contacts'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(250), nullable=True, default=None)
email = db.Column(db.String(250), nullable=False)
company_id = db.Column(db.Integer, db.ForeignKey('companies.id'), nullable=True, default=None)
company = relationship('Company')
organization_id = db.Column({Import Company.organization_id as eager})
The last line is of course garbage, but it's to show the idea:
I'd like to have the value "organization_id" available in Contact, even though it's not present in the table "contacts", but since it's present in "companies", is there a way to ask SQLAlchemy to load the value from "companies" via a JOIN, and affect it to "contacts" as a read-only value?
That way, when I search for a contact, for instance :
contact = Contact.query.filter(Contact.email = 'test#test.com').first()
print(contact.organization_id) # => 1
Thank you.
You can use the hybrid_property decorator to define an attribute on your class:
class Contact(db.Model):
...
#hybrid_property
def organization_id(self):
return self.company.organization_id if self.company else None
Using contact.organization_id will load the company using the foreign key relationship.
So I'm building an app and I'm trying to save new changes to my database but when I try to commit the changes in the flask using db.session.commit() it returns me the following error:
sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'products.country_id' could not find table 'countries' with which to generate a foreign key to target column 'id'
In my models.py I have the following:
from app import db
from . import db
from datetime import datetime
def now():
return datetime.now()
class Countries(db.Model):
__tablename__ = 'countries'
__table_args__ = {'schema': 'products_data'}
id = db.Column(db.Integer, primary_key=True, unique=True, autoincrement=True)
name = db.Column(db.String(255))
code = db.Column(db.String(45))
def __repr__(self):
return f'Id {self.id}'
class Categories(db.Model):
__tablename__ = 'categories'
__table_args__ = {'schema': 'products_data'}
id = db.Column(db.Integer, primary_key=True, unique=True, autoincrement=True)
name = db.Column(db.String(255))
def __repr__(self):
return f'Id {self.id}'
class Brands(db.Model):
__tablename__ = 'brands'
__table_args__ = {'schema': 'products_data'}
id = db.Column(db.Integer, primary_key=True, unique=True, autoincrement=True)
name = db.Column(db.String(255))
logo = db.Column(db.String(5000))
feed = db.Column(db.String(5000))
feed_type = db.Column(db.String(45))
category_id = db.Column(db.Integer, db.ForeignKey('categories.id'))
country_id = db.Column(db.Integer, db.ForeignKey('countries.id'))
awinmid = db.Column(db.Integer)
def __repr__(self):
return f'Id {self.id}'
class Products(db.Model):
__tablename__ = 'products'
__table_args__ = {'schema': 'products_data'}
id = db.Column(db.Integer, primary_key=True, unique=True, autoincrement=True)
name = db.Column(db.String(255))
url = db.Column(db.Text)
category_id = db.Column(db.Integer, db.ForeignKey('categories.id'))
country_id = db.Column(db.Integer, db.ForeignKey('countries.id'))
price = db.Column(db.Float)
currency = db.Column(db.String(45))
discount_price = db.Column(db.Float)
shipping = db.Column(db.Float)
brand_id = db.Column(db.Integer, db.ForeignKey('brands.id'))
Am I doing anything wrong when associating a column in products with a foreign key? This is the first time I encounter this error so I'm really lost on what to do right now.
To fix I just added the schema to the db.ForeignKey and it worked
Example:
db.ForeignKey('products_data.countries.id')
PS:
Not my idea. Just wanted to post the answer in case someone visits the post later with the same problem.
Gord Thompson thanks for the help!
First of all, I don t see any table Categories. Secondly, you copy pasted your schema from the Products table into your Countries one.
PS: By default sqlalchemy gives the tables the name of the class (lower cased). So your __tablename__='products' does nothing actually.
EDIT:
The problem with your code lies in how you set the __table_args__ attribute. You assign an object to it, which by their specifications is wrong.
Take a look at the following example and modify your code accordingly
__table_args__ = ({'schema': 'products_data'})
Also for further reference, take a look at this https://docs.sqlalchemy.org/en/13/orm/extensions/declarative/table_config.html
I am inexperienced programmer. I'd like to add one-to-one relationship CurrencyDefault (that value will be assigned to the field in FlaskForm) between User and Currency:
class User(UserMixin, db.Model):
id = db.Column(db.Integer, db.Sequence('user_id_seq'), primary_key=True)
username = db.Column(db.String(64), index=True, unique=True)
email = db.Column(db.String(64), index=True, unique=True)
pswd_hash = db.Column(db.String(128))
expenses = db.relationship('Expense', backref='user')
currency = db.relationship('Currency', backref='user')
curr_default = ?
# ...
class Currency(db.Model):
id = db.Column(db.Integer, db.Sequence('expense_id_seq'), primary_key=True)
abbr = db.Column(db.String(10))
name = db.Column(db.String(64))
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
default = ?
# ...
What I want to achieve is to assign to each user.id one currency.id (one-to-one)
I'd like to ask for some advice what is the best way to make it.
After considering the problem I have some ideas like:
Association Table with uselist=False relationship,
Create a new class CurrencyDefault(id, user_id, currency_id),
Or maybe there is other, better way to achieve it?
I'm very curious of your point of view on this problem.
Implementing solution:
This is how my classes look like now:
class User(UserMixin, db.Model):
id = db.Column(db.Integer, db.Sequence('user_id_seq'), primary_key=True)
username = db.Column(db.String(64), index=True, unique=True)
email = db.Column(db.String(64), index=True, unique=True)
pswd_hash = db.Column(db.String(128))
currency_default_choice = db.Column(db.Integer, b.ForeignKey('currency.id'))
expenses = db.relationship('Expense', backref='user')
currency = db.relationship('Currency', backref='user', foreign_keys="Currency.user_id")
# currency_default = db.relationship(
# 'Currency',
# foreign_keys='User.currency_default_choice',
# backref='currency_default',
# uselist=False,
# )
# ...
class Currency(db.Model):
id = db.Column(db.Integer, db.Sequence('expense_id_seq'), primary_key=True)
abbr = db.Column(db.String(10), b.ForeignKey('currency_official_abbr.abbr'))
name = db.Column(db.String(64))
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
currency_default = db.relationship(
'User',
foreign_keys='User.currency_default_choice',
backref='currency_default',
uselist=False,
)
The first problem I find is that I can set Currency.id object created by other_user as currency_default_choice. How to restrict currency_default_choice only to the <Currency> that was created by this user?
What is the difference between setting relationship having foreign key in User class (currency_default_choice = db.Column(db.Integer, b.ForeignKey('currency.id'))) with:
class Currency(db.Model):
# ...
currency_default = db.relationship(
'User',
foreign_keys='User.currency_default_choice',
backref='currency_default',
uselist=False,
)
and setting this relationship on User side with:
class User(db.Model):
# ...
currency_default = db.relationship(
'Currency',
foreign_keys='User.currency_default_choice',
backref='currency_default',
uselist=False,
)
Ad.2. What seems to me is that there is no difference between these two ways because the backref parameter implicates bidirectional behavior so it doesn't matter if I placed db.relationship() in User or Currency class. Is it correct?
Using Python shell I added value to the User.currency_default
>>> app = create_app()
>>> app.app_context().push()
>>> admin = User.query.filter_by(username='admin').first()
<User(id= 1, username = admin, email = admin#admin.com)
>>> currency = Currency.query.filter_by(user=admin)
>>> currency
<flask_sqlalchemy.BaseQuery object at 0x03EA05D0>
>>> currency[0].id
1
>>> admin.currency_default = currency[0]
>>> db.session.commit()
>>> currency[0].currency_default
<User(id= 1, username = admin, email = admin#admin.com)
>>> admin.currency_default_choice
1
and then using Admin Panel after running flask run I wanted to remove introduced value but I got error that I don't understand. Why there is circular dependency between (Currency.currency_default),(User.currency_default) and (User.currency)? I don't understand what is happening. How to fix it?
sqlalchemy.exc.CircularDependencyError: Circular dependency detected.
(ProcessState(OneToManyDP(Currency.currency_default),
<Currency at 0x46542b0>, delete=False),
ProcessState(ManyToOneDP(User.currency_default),
<User at 0x4669b10>, delete=False),
SaveUpdateState(<Currency at 0x46542b0>),
ProcessState(OneToManyDP(User.currency), <User at 0x4669b10>, delete=False),
SaveUpdateState(<User at 0x4669b10>))
hi i have a many to many relationship between a user and a group.and i will like to add a user with many groups in my database.how do i do that if my database is as follows
user_group_table = Table('tg_user_group', metadata,
Column('user_id', Integer, ForeignKey('tg_user.user_id',
onupdate="CASCADE", ondelete="CASCADE")),
Column('group_id', Integer, ForeignKey('tg_group.group_id',
onupdate="CASCADE", ondelete="CASCADE"))
)
class Group(DeclarativeBase):
"""
Group definition for :mod:`repoze.what`.1
Only the ``group_name`` column is required by :mod:`repoze.what`.
"""
__tablename__ = 'tg_group'
#{ Columns
group_id = Column(Integer, autoincrement=True, primary_key=True)
group_name = Column(Unicode(16), unique=True, nullable=False)
display_name = Column(Unicode(255))
created = Column(DateTime, default=datetime.now)
#{ Relations
users = relation('User', secondary=user_group_table, backref='groups')
#{ Special methods
def __repr__(self):
return '<Group: name=%s>' % self.group_name
def __unicode__(self):
return self.group_name
#}
class User(DeclarativeBase):
"""
User definition.
This is the user definition used by :mod:`repoze.who`, which requires at
least the ``user_name`` column.
"""
__tablename__ = 'tg_user'
#{ Columns
user_id = Column(Integer, autoincrement=True, primary_key=True)
user_name = Column(Unicode(16), unique=True, nullable=False)
email_address = Column(Unicode(255), unique=True, nullable=False,
info={'rum': {'field':'Email'}})
display_name = Column(Unicode(255))
_password = Column('password', Unicode(80),
info={'rum': {'field':'Password'}})
created = Column(DateTime, default=datetime.now)
doing it this way however gives me an error
#expose()
def user_save(self, **kw):
user = User()
user.user_name = kw['user_name']
user.display_name = kw['display_name']
user.email_address = kw['Email']
user._password = kw['password']
user.groups.extend(kw['groups'])
DBSession.add(user)
DBSession.flush()
flash("successfully saved...")
flash(user)
redirect("/user_new")
pls help me solve this.thanks in advance
I believe the answer is in the error message that you havn't posted in the question. user.groups is a list of Group objects, while you assign a list of strings(?) got from form to it. Also I see no explicit DBSession.commit() call. Are you sure TurboGears will do it for you?