SQLAlchemy 设置默认 nullable=False

Question

I'm using SQLAlchemy for Flask to create some models. The problem is, nearly all my columns need nullable=False , so I'm looking for a way to set this option as default when creating a column. Surely I could add them manually (as a Vim exercise), but I just don't feel like it today. For a reference, this is how my setup ( models.py ) looks like:

from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     username = db.Column(db.String(80), nullable=False)

and many more. Is there a simple way of doing this?

Thanks in advance.

Answer 1

just create a wrapper that sets it

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

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

using functools.partial as recommended in the comments

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

Answer 2

As Column is a class, subclassing seems a lot more extensible.

from sqlalchemy.sql.schema import Column as Col
    
class Column(Col):
    def __init__(self, *args, **kwargs):
        kwargs.setdefault('nullable', False)
        super().__init__(*args, **kwargs)

Answer 3

The accepted answer creates a wrapper for a nullable = True column called NullColumn , which is already what Column does by default. The question asks to set nullable = False (not True ) as the default when creating a column.

from sqlalchemy import Column as Col

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

This function returns a Column with nullable = False by default, which can also be overwritten with nullable = True if needed (unlike the functools.partial solution).