How to use `migrate()` in Peewee

Question

I am new in peewee and I am very confused about migration. I tried the examples in the official documentation, and I got the results as follows:

from playhouse.migrate import *
from peewee import *

my_db = SqliteDatabase('my_database.db')
migrator = SqliteMigrator(my_db)

from peewee import *

database = SqliteDatabase('my_database.db')

class BaseModel(Model):
    class Meta:
        database = database

class Product(BaseModel):
    name = TextField()

    class Meta:
        table_name = 'product'

with my_db:
    my_db.create_tables([Product,])

Product.create(name = 'Big Peach')

price_field = IntegerField(default=0)
migrate(migrator.add_column('product', 'price', price_field))
db = migrator.database
columns = db.get_columns('product')
print(columns)

Here's what I got and the field of 'price' was added, indicating that migrated () is doing well:

[ColumnMetadata(name='id', data_type='INTEGER', null=False, primary_key=True, table='product', default=None), ColumnMetadata(name='name', data_type='TEXT', null=False, primary_key=False, table='product', default=None), ColumnMetadata(name='price', data_type='INTEGER', null=False, primary_key=False, table='product', default=None)]

Now the problem is that when I call Product.price ,

query = Product.get(Product.name == 'Big Peach')
print(query.price)

the following result appears:

'Product' object has no attribute 'price'

I've tried another way to do this, in the command line:

python -m pwiz -e sqlite my_database.db

I got this:

from peewee import *

database = SqliteDatabase('my_database.db')

class UnknownField(object):
    def __init__(self, *_, **__): pass

class BaseModel(Model):
    class Meta:
        database = database

class Product(BaseModel):
    name = CharField()
    price = IntegerField()

    class Meta:
        table_name = 'product'   

I can use these to replace the previous Model, but there's no need to migrate() . So, my confusion is how to call the new field added by using migrate() in ONE .py file.

Answer 1

It's unusual to do this online:

1. declare a model/schema
2. migrate it
3. use the new schema

Because if you know you need a price field just put it on the model class from the start.

If you really need to do this, then you can call this after you've run the migration:

Product._meta.add_field('price', price_field)