On Wed, Aug 29, 2018 at 2:17 PM, <[email protected]> wrote:
> Hi !
>
> I'm using Python 3.6.5, Flask 1.0.2, SQLAlchemy 1.0.5 and I want to define
> an attribute as a maximum between other two, based on flask-admin hybrid
> property example:
>
>
> from flask import Flask
> from flask_sqlalchemy import SQLAlchemy
> from sqlalchemy.ext.hybrid import hybrid_property
>
> import flask_admin as admin
> from flask_admin.contrib import sqla
>
> from sqlalchemy.sql.expression import func
>
> # Create application
> app = Flask(__name__)
>
> # Create dummy secrey key so we can use sessions
> app.config['SECRET_KEY'] = '123456790'
>
> # Create in-memory database
> app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///sample_db_2.sqlite'
> app.config['SQLALCHEMY_ECHO'] = True
> db = SQLAlchemy(app)
>
>
> # Flask views
> @app.route('/')
> def index():
> return '<a href="/admin/">Click me to get to Admin!</a>'
>
>
> class Screen(db.Model):
> __tablename__ = 'screen'
> id = db.Column(db.Integer, primary_key=True)
> width = db.Column(db.Integer, nullable=False)
> height = db.Column(db.Integer, nullable=False)
>
> @hybrid_property
> def max(self):
> return max(self.height, self.width)
when you use a hybrid_property you need to ensure the expression you
are returning is also suitable as a SQL expression, so your code
should read:
class Screen(db.Model):
__tablename__ = 'screen'
id = db.Column(db.Integer, primary_key=True)
width = db.Column(db.Integer, nullable=False)
height = db.Column(db.Integer, nullable=False)
@hybrid_property
def max(self):
return max(self.height, self.width)
@max.expression
def max(cls):
return func.max(cls.height, cls.width)
>
> class ScreenAdmin(sqla.ModelView):
> """ Flask-admin can not automatically find a hybrid_property yet. You
> will
> need to manually define the column in
> list_view/filters/sorting/etc."""
> column_list = ['id', 'width', 'height', 'max']
> column_sortable_list = ['id', 'width', 'height', 'max']
>
> # Flask-admin can automatically detect the relevant filters for hybrid
> properties.
> column_filters = ('max', )
>
>
> # Create admin
> admin = admin.Admin(app, name='Example: SQLAlchemy2',
> template_mode='bootstrap3')
> admin.add_view(ScreenAdmin(Screen, db.session))
>
> if __name__ == '__main__':
>
> # Create DB
> db.create_all()
>
> # Start app
> app.run(debug=True)
>
>
> But it fails, raising this error:
>
> raise TypeError("Boolean value of this clause is not defined")
>
>
> Traceback:
>
> /home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/flask_sqlalchemy/__init__.py:794:
> FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant
> overhead and will be disabled by default in the future. Set it to True or
> False to suppress this warning.
> 'SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and '
> Traceback (most recent call last):
> File "app.py", line 49, in <module>
> admin.add_view(ScreenAdmin(Screen, db.session))
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/flask_admin/contrib/sqla/view.py",
> line 329, in __init__
> menu_icon_value=menu_icon_value)
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/flask_admin/model/base.py",
> line 804, in __init__
> self._refresh_cache()
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/flask_admin/model/base.py",
> line 881, in _refresh_cache
> self._list_columns = self.get_list_columns()
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/flask_admin/model/base.py",
> line 1022, in get_list_columns
> excluded_columns=self.column_exclude_list,
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/flask_admin/contrib/sqla/view.py",
> line 531, in get_column_names
> column, path = tools.get_field_with_path(self.model, c)
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/flask_admin/contrib/sqla/tools.py",
> line 150, in get_field_with_path
> value = getattr(current_model, attribute)
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/sqlalchemy/ext/hybrid.py",
> line 867, in __get__
> return self._expr_comparator(owner)
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/sqlalchemy/ext/hybrid.py",
> line 1066, in expr_comparator
> owner, self.__name__, self, comparator(owner),
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/sqlalchemy/ext/hybrid.py",
> line 1055, in _expr
> return ExprComparator(cls, expr(cls), self)
> File "app.py", line 34, in number_of_pixels
> return max(self.width,self.height)
> File
> "/home/bibo/usr/miniconda/envs/otroflask/lib/python3.6/site-packages/sqlalchemy/sql/elements.py",
> line 2975, in __bool__
> raise TypeError("Boolean value of this clause is not defined")
>
>
> I've tried with the max sqlalchemy function:
>
>
> return func.max(self.height, self.width)
>
>
> But it returns literally a function not a value.
>
>
> I also tried to use concept of this answer, without success.
>
>
> Any idea?
>
>
> Thanks!
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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