nullable_enum.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import Enum, String

import flask_admin as admin
from flask_admin.contrib import sqla


# 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:///a_sample_database.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 Pet(db.Model):
    __tablename__ = 'pet'
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    petname = db.Column(String(20), nullable=False, unique=True)
    gender_if_known = db.Column(Enum('Male', 'Female'))


class PetAdmin(sqla.ModelView):
    column_editable_list = ('gender_if_known', )

# Create admin
admin = admin.Admin(app, name='Example: SQLAlchemy2', template_mode='bootstrap3')

admin.add_view(PetAdmin(Pet, db.session))

if __name__ == '__main__':

    # Create DB
    db.drop_all()
    db.create_all()
    db.session.add(Pet(petname='Flipper', gender_if_known='Male'))
    db.session.add(Pet(petname='Fifi'))
    db.session.commit()

    # Start app
    app.run(debug=True)

Demonstrates this issue in flask-admin.