tipi enumerati Python sono direttamente accettabili dal tipo SQLAlchemy Enum come di SQLAlchemy 1.1:
import enum
class MyEnum(enum.Enum):
one = 1
two = 2
three = 3
class MyClass(Base):
__tablename__ = 'some_table'
id = Column(Integer, primary_key=True)
value = Column(Enum(MyEnum))
noti che precede, i valori di stringa "uno", "due", "tre" vengono mantenute, non il valori interi.
Per le versioni più vecchie di SQLAlchemy, ho scritto un post che crea il suo proprio tipo enumerato (http://techspot.zzzeek.org/2011/01/14/the-enum-recipe/)
from sqlalchemy.types import SchemaType, TypeDecorator, Enum
from sqlalchemy import __version__
import re
if __version__ < '0.6.5':
raise NotImplementedError("Version 0.6.5 or higher of SQLAlchemy is required.")
class EnumSymbol(object):
"""Define a fixed symbol tied to a parent class."""
def __init__(self, cls_, name, value, description):
self.cls_ = cls_
self.name = name
self.value = value
self.description = description
def __reduce__(self):
"""Allow unpickling to return the symbol
linked to the DeclEnum class."""
return getattr, (self.cls_, self.name)
def __iter__(self):
return iter([self.value, self.description])
def __repr__(self):
return "<%s>" % self.name
class EnumMeta(type):
"""Generate new DeclEnum classes."""
def __init__(cls, classname, bases, dict_):
cls._reg = reg = cls._reg.copy()
for k, v in dict_.items():
if isinstance(v, tuple):
sym = reg[v[0]] = EnumSymbol(cls, k, *v)
setattr(cls, k, sym)
return type.__init__(cls, classname, bases, dict_)
def __iter__(cls):
return iter(cls._reg.values())
class DeclEnum(object):
"""Declarative enumeration."""
__metaclass__ = EnumMeta
_reg = {}
@classmethod
def from_string(cls, value):
try:
return cls._reg[value]
except KeyError:
raise ValueError(
"Invalid value for %r: %r" %
(cls.__name__, value)
)
@classmethod
def values(cls):
return cls._reg.keys()
@classmethod
def db_type(cls):
return DeclEnumType(cls)
class DeclEnumType(SchemaType, TypeDecorator):
def __init__(self, enum):
self.enum = enum
self.impl = Enum(
*enum.values(),
name="ck%s" % re.sub(
'([A-Z])',
lambda m:"_" + m.group(1).lower(),
enum.__name__)
)
def _set_table(self, table, column):
self.impl._set_table(table, column)
def copy(self):
return DeclEnumType(self.enum)
def process_bind_param(self, value, dialect):
if value is None:
return None
return value.value
def process_result_value(self, value, dialect):
if value is None:
return None
return self.enum.from_string(value.strip())
if __name__ == '__main__':
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, create_engine
from sqlalchemy.orm import Session
Base = declarative_base()
class EmployeeType(DeclEnum):
part_time = "P", "Part Time"
full_time = "F", "Full Time"
contractor = "C", "Contractor"
class Employee(Base):
__tablename__ = 'employee'
id = Column(Integer, primary_key=True)
name = Column(String(60), nullable=False)
type = Column(EmployeeType.db_type())
def __repr__(self):
return "Employee(%r, %r)" % (self.name, self.type)
e = create_engine('sqlite://', echo=True)
Base.metadata.create_all(e)
sess = Session(e)
sess.add_all([
Employee(name='e1', type=EmployeeType.full_time),
Employee(name='e2', type=EmployeeType.full_time),
Employee(name='e3', type=EmployeeType.part_time),
Employee(name='e4', type=EmployeeType.contractor),
Employee(name='e5', type=EmployeeType.contractor),
])
sess.commit()
print sess.query(Employee).filter_by(type=EmployeeType.contractor).all()
secondo link non si apre più – MajesticRa
@MajesticRa: grazie per il suggerimento, ho rimosso il collegamento. Non è più rilevante in ogni caso. Ognuno dovrebbe essere aggiornato a 0.6 anni fa;) – Wolph