Initializing Python class object with external data

Question

Suppose a "person" class contains name, age and phone number.

When creating a person object, I would like to set phone number by looking up an external phone book rather than explicitly passing a phone number.

Option 1: Store phone book as a class variable

class person():

    phonebook = {}

    def __init__(self, name, age):
        self.name = name
        self.age = age
        self.phone = self.phonebook[self.name]

person.phonebook = {'dan':1234}
dan = person('dan', 30)

Option 2: Create a class object without phone number then have a separate function to load it.

class person():

    def __init__(self, name, age):
        self.name = name
        self.age = age

    def loadphone(self, phone):
        self.phone = phone

phonebook = {'dan':1234}
dan = person('dan',30)
dan.loadphone(phonebook['dan'])

Both solutions do not seem optimal. Option 1, every person carries a phone book (unnecessarily). Option 2 requires 2-step initialization.

Is there a better way to create a person object without 1) explicitly passing a phone number or phone book during initialization, 2) storing phone book as a class variable, and 3) requiring a multi-step initialization?

Option 1 would have everyone carrying the same phonebook in python. — cssko
– cssko, Commented Jul 20, 2017 at 17:37
"Option 1, every person carries a phone book (unnecessarily)" This is not true, every instance has access to a single phone book which is stored as data on the class (and lookup on an instance will check the class dictionary if not found on the instance). — Jared Goguen
– Jared Goguen, Commented Jul 20, 2017 at 17:37
"every person carries a phone book (unnecessarily)" - Incorrect. Every person has accesses to the phone-book, but not every person carries a phone-book. The class object is what stores the phone-book. — Chris
– Chris, Commented Jul 20, 2017 at 17:37
In option 1, the phonebook belongs to the class. The instances of a class have access to it's namespace, though. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jul 20, 2017 at 17:37

Chris · Accepted Answer · 2017-07-20 23:15:06Z

3

As discussed in this post, defining a variable outside of any methods in the class, while still being defined in a class makes it a static variable, such as the one you have:

class person():

    phonebook = {}

This means that there is a single phonebook which all instances of the class refer to

person.phonebook{'dave':1234, 'joey':5678}

dave = person('dave', 30)
joey = person('joey', 23)

There is still only the one universal phonebook that all instances refer to. The one thing to change in that code is that you should not define it as self.phonebook['dave'] so it should look like

class person():

    phonebook = {}

    def __init__(name, age):
        self.name = name
        self.age = age
        self.number = phonebook[name]

edited Jul 20, 2017 at 23:15

Chris

23.2k8 gold badges63 silver badges91 bronze badges

answered Jul 20, 2017 at 17:46

Professor_Joykill

9993 gold badges8 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

cssko · Accepted Answer · 2017-07-20 17:42:47Z

1

Are you wanting to optionally define a phone number for a Person? You could do something like below:

class Person():
    def __init__(self, name, age, phone=None):
        self.name = name
        self.age = age
        self.phone = phone

dan = Person('dan',30, phone=1234)
stan = Person('stan', 60)

answered Jul 20, 2017 at 17:42

cssko

3,0551 gold badge20 silver badges21 bronze badges

Comments

juanpa.arrivillaga · Accepted Answer · 2017-07-20 18:12:23Z

0

Firstly, as for me, it's too wide question and very depend on task. In one case you can access to PhoneBook, in another - it's bad idea (e.g. PhoneBook load data from server and creating 1000 of Person will produce 1000 requests).

Secondary, their is next approach:

class BasicPerson():
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def ToString(self):
        return('some code')

class PersonWithPhone():
    def __init__(self, basicPerson, phone):
        self.basicPerson = basicPerson
        self.phone = phone

    def ToString(self):
        return('another code ' + self.basicPerson.ToString())

person = PersonWithPhone(BasicPerson('', ''), '11111')

It's just example and may seems useless, but in many situations you can extract some core actions (ToString, for example) and than wrote small decorators that expand each other.

edited Jul 20, 2017 at 18:12

juanpa.arrivillaga

97.6k14 gold badges141 silver badges190 bronze badges

answered Jul 20, 2017 at 18:11

user3797387

2 Comments

Professor_Joykill Over a year ago

Why not just make PersonWithPhone a child class and use the super method.

user3797387 Over a year ago

Because you can easily pass some PersonWithHomeAddress(WithMobile(WithTwitter())) and than wrap it into DBStoredPerson. Inheritance are provide same result only in simple cases.

Collectives™ on Stack Overflow

Initializing Python class object with external data

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related