Can anyone describe how to return objects from a method on which further methods and attributes can be accessed?
Example:
pizza = PizzaHut()
order = pizza.order()
print order.order_number
order.cancel()
5 Answers
Create an Order class with appropriate methods and properties. After that, you'll be able to return an instance of this class from PizzaHut.order() method.
class Order(object):
def __init__(self, number, amount):
self.number = number
self.amount = amount
print self
def __str__(self):
return "Order #%s: amount = %s" % (self.number, self.amount)
@property
def order_number(self):
return self.number
def cancel(self):
self.amount = 0
print "Order is cancelled."
print self
class PizzaHut(object):
def __init__(self, price):
self.price = price
def order(self):
return Order(42, self.price)
pizza = PizzaHut(4.99)
order = pizza.order()
print order.order_number
order.cancel()
Python 3 version
class Order:
def __init__(self, number, amount):
self.number = number
self.amount = amount
print(self)
def __str__(self):
return f'Order #{self.number}: amount = {self.amount}'
@property
def order_number(self):
return self.number
def cancel(self):
self.amount = 0
print('Order is cancelled.')
print(self)
class PizzaHut:
def __init__(self, price):
self.price = price
def order(self):
return Order(42, self.price)
pizza = PizzaHut(4.99)
order = pizza.order()
print(order.order_number)
order.cancel()
5 Comments
Delete Me
Thanks, can you tell me what
def __str__ does?
Eugene Naydenov
Sure. This is a special method which provides a string representation of object. See: docs.python.org/2/reference/datamodel.html#object.__str__
Caleb
Do we need the "object" in the class Order(object) line? What does it do?
Caleb
Note: setting the object subclass is unnecessary in Python > 3.x, see: stackoverflow.com/questions/2588628/…
Eugene Naydenov
@Caleb You're right. Also nowadays I would better use string interpolation in the
__str__ instead of old string formatting using %. :) And also all the prints should function in Python 3. Though this is out of the scope of the question's purpose.you can use Namedtuplesin in python.
# Using namedtuple is way shorter than
# defining a class manually:
>>> from collections import namedtuple
>>> Car = namedtuple('Car', 'color mileage')
# Our new "Car" class works as expected:
>>> my_car = Car('red', 3812.4)
>>> my_car.color
'red'
>>> my_car.mileage
3812.4
# We get a nice string repr for free:
>>> my_car
Car(color='red' , mileage=3812.4)
# Like tuples, namedtuples are immutable:
>>> my_car.color = 'blue'
AttributeError: "can't set attribute"
1 Comment
Community
Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.
class Order:
def __init__(self, number):
self.order_number = number
class PizzaHut:
def __init__(self):
self.order = Order(1234)
def order(self):
return self.order
1 Comment
jonrsharpe
I'm not sure a restaurant that can only handle one order would stay in business long...
This is how to return back the object from a method
class Order(object):
def __init__(self, number, amount):
self.number = number
self.amount = amount
def cancel(self):
self.amount = 0
return self #here you return back the object
None, in the trivial case) whose own attributes (including methods) can then be accessed. What exactly is your question?!