CODEWITHSUNDEEP
pythonoop
James Kang
James Kang

Reputation: 509

Initializing Python class object with external data

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?

Upvotes: 0

Views: 575

Answers (3)

Professor_Joykill
Professor_Joykill

Reputation: 989

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]

Upvotes: 3

user3797387
user3797387

Reputation:

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.

Upvotes: 0

cssko
cssko

Reputation: 3045

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)

Upvotes: 1

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