Soy nuevo en Python, y quería asegurarse de que hizo caso omiso de __eq__
__hash__
y correctamente, a fin de no causar errores dolorosos más tarde: (. Estoy usando Google App Engine)Python: ¿Es esta una buena forma de anular __eq__ y __hash__?
class Course(db.Model):
dept_code = db.StringProperty()
number = db.IntegerProperty()
title = db.StringProperty()
raw_pre_reqs = db.StringProperty(multiline=True)
original_description = db.StringProperty()
def getPreReqs(self):
return pickle.loads(str(self.raw_pre_reqs))
def __repr__(self):
title_msg = self.title if self.title else "Untitled"
return "%s %s: %s" % (self.dept_code, self.number, title_msg)
def __attrs(self):
return (self.dept_code, self.number, self.title, self.raw_pre_reqs, self.original_description)
def __eq__(self, other):
return isinstance(other, Course) and self.__attrs() == other.__attrs()
def __hash__(self):
return hash(self.__attrs())
Un tipo un poco más complicado:
class DependencyArcTail(db.Model):
''' A list of courses that is a pre-req for something else '''
courses = db.ListProperty(db.Key)
''' a list of heads that reference this one '''
forwardLinks = db.ListProperty(db.Key)
def __repr__(self):
return "DepArcTail %d: courses='%s' forwardLinks='%s'" % (id(self), getReprOfKeys(self.courses), getIdOfKeys(self.forwardLinks))
def __eq__(self, other):
if not isinstance(other, DependencyArcTail):
return False
for this_course in self.courses:
if not (this_course in other.courses):
return False
for other_course in other.courses:
if not (other_course in self.courses):
return False
return True
def __hash__(self):
return hash((tuple(self.courses), tuple(self.forwardLinks)))
Todo se ve bien?
actualizado para reflejar los comentarios de Alex @
class DependencyArcTail(db.Model):
''' A list of courses that is a pre-req for something else '''
courses = db.ListProperty(db.Key)
''' a list of heads that reference this one '''
forwardLinks = db.ListProperty(db.Key)
def __repr__(self):
return "DepArcTail %d: courses='%s' forwardLinks='%s'" % (id(self), getReprOfKeys(self.courses), getIdOfKeys(self.forwardLinks))
def __eq__(self, other):
return isinstance(other, DependencyArcTail) and set(self.courses) == set(other.courses) and set(self.forwardLinks) == set(other.forwardLinks)
def __hash__(self):
return hash((tuple(self.courses), tuple(self.forwardLinks)))
Se ve bien. Gracias. –
@Rosarch, de nada! –
@Alex: ¿ese hash no depende del orden de los elementos en 'tuple (set (self.courses))', que podría ser algo arbitrario? –