SQLAlchemy set default nullable=False

This post provides several solutions to set the default value of the nullable parameter to False when creating a column in SQLAlchemy. Here's a summary of the suggested approaches:

Method 1: Create a Wrapper Function

def NullColumn(*args, **kwargs):
    kwargs["nullable"] = kwargs.get("nullable", True)
    return db.Column(*args, **kwargs)

...
username = NullColumn(db.String(80))

Here, a wrapper function called NullColumn is defined. It takes arguments and keyword arguments, sets the nullable parameter to True by default, and returns a column object using the db.Column function.

Method 2: Utilize functools.partial

from functools import partial
NullColumn = partial(Column, nullable=True)

This approach utilizes the functools.partial function to create a partial function called NullColumn. This partial function sets the nullable parameter to True by default and can be used as a drop-in replacement for the Column function.

Method 3: Subclassing Column

from sqlalchemy import Column as Col

class Column(Col):
    def __init__(self, *args, **kwargs):
        kwargs.setdefault('nullable', False)
        super().__init__(*args, **kwargs)

In this method, a subclass called Column is created that inherits from SQLAlchemy's Column class. The __init__ method of this subclass sets the nullable parameter to False by default. This allows you to create columns with nullable=False without explicitly specifying it.

Method 4: Using Typing Support in SQLAlchemy 2.0

import sqlalchemy as sa
from sqlalchemy import orm
from sqlalchemy.orm import Mapped, mapped_column

class Base(orm.DeclarativeBase):
    pass

class User(Base):
    __tablename__ = 't29522557'

    id: Mapped[int] = mapped_column(primary_key=True)
    name: Mapped[str]
    title: Mapped[str | None]

With the introduction of typing support in SQLAlchemy 2.0, you can enforce non-nullability by not declaring the column's type as optional. In the example provided, the id and name columns have non-nullable types, while the title column is nullable because its type is declared as str | None.

Method 5: Set Default Value to False

from sqlalchemy import Column as Col

def Column(*args, **kwargs):
    kwargs.setdefault('nullable', False)
    return Col(*args, **kwargs)

This approach creates a new Column function that sets the nullable parameter to False by default. It acts as a drop-in replacement for the default Column function and ensures that all columns created using this function will be non-nullable unless explicitly set to True.

By utilizing one of these methods, you can easily set the default value of the nullable parameter to False when creating columns in SQLAlchemy, ensuring data integrity and preventing null values in your database tables.