Defining SQLAlchemy enum column with Python enum raises "ValueError: not a valid enum"

Question

I am trying to follow this example to have an enum column in a table that uses Python’s Enum type. I define the enum then pass it to the column as shown in the example, but I get ValueError: <enum 'FruitType'> is not a valid Enum. How do I correctly define a SQLAlchemy enum column with a Python enum?

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import enum

app = Flask(__name__)
db = SQLAlchemy(app)

class FruitType(enum.Enum):
    APPLE = "Crunchy apple"
    BANANA = "Sweet banana"

class MyTable(db.Model):
    id = db.Column(db.Integer, primary_key = True)
    fruit_type = db.Column(enum.Enum(FruitType))

File "why.py", line 32, in <module>
    class MyTable(db.Model):
  File "why.py", line 34, in MyTable
    fruit_type = db.Column(enum.Enum(FruitType))
  File "/usr/lib/python2.7/dist-packages/enum/__init__.py", line 330, in __call__
    return cls.__new__(cls, value)
  File "/usr/lib/python2.7/dist-packages/enum/__init__.py", line 642, in __new__
    raise ValueError("%s is not a valid %s" % (value, cls.__name__))
ValueError: <enum 'FruitType'> is not a valid Enum

Asked By: Digital

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Source

Answer 1

The column type should be sqlalchemy.types.Enum. You’re using the Python Enum type again, which was valid for the value but not the column type. Back in 2016, when the question was written, this was necessary:

class MyTable(db.Model):
    id = db.Column(db.Integer, primary_key = True)
    fruit_type = db.Column(db.Enum(FruitType))

However, this is not the case anymore.

Answered By: r-m-n

Defining SQLAlchemy enum column with Python enum raises "ValueError: not a valid enum"

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