python call class instance from string

Question

I declared a class:

class Persons:

    def __init__(self, person_id, value:
        self.person_id = person_id
        self.value = value

and I created an instance:

p1 = Persons("p1", "0")

Now I want to take a string from an input that will tell me the person's id, and then switch it's value from "0" to "1":

inp_string = input("Which person should have its value changed?")
name = "p" + inp_string
name.value = "1"

So I want to change the string 'name' to the class instance of the same name. I don't mind to select the person by its name (p1) or by it's person_id ("p1"). Either way is good.

awesoon · Accepted Answer · 2018-10-11 05:55:12Z

2

Just create a dict of persons:

persons_dict = {'p1': Persons("p1", "0")}
inp_string = input("Which person should have its value changed?")
persons_dict[inp_string].value = '1'

inp_string should be p1

You can easily wrap it with a class:

In [32]: class Person:
    ...:     def __init__(self, person_id, value):
    ...:         self.person_id = person_id
    ...:         self.value = value
    ...:     def __repr__(self):
    ...:         return f'Person<person_id: {self.person_id}, value: {self.value}>'
    ...:

In [33]: class Persons:
    ...:     def __init__(self):
    ...:         self.persons = {}
    ...:     def add_person(self, person_id, value):
    ...:         if person_id in self.persons:
    ...:             raise ValueError('person_id already exists')
    ...:         self.persons[person_id] = Person(person_id, value)
    ...:     def get_person_by_id(self, person_id):
    ...:         return self.persons[person_id]
    ...:     def __repr__(self):
    ...:         return f'Persons<{self.persons}>'
    ...:

In [34]: persons = Persons()

In [35]: persons.add_person('p1', '0')

In [36]: persons.add_person('p2', '2')

In [37]: persons
Out[37]: Persons<{'p1': Person<person_id: p1, value: 0>, 'p2': Person<person_id: p2, value: 2>}>

In [38]: persons.get_person_by_id('p1').value = '1'

In [39]: persons
Out[39]: Persons<{'p1': Person<person_id: p1, value: 1>, 'p2': Person<person_id: p2, value: 2>}>

edited Oct 11, 2018 at 5:55

answered Oct 11, 2018 at 5:34

awesoon

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5 Comments

Domiinic Over a year ago

It has to be a Class. That's the restriction.

Domiinic Over a year ago

Python version 3.4 does not support a 'F' prefix

awesoon Over a year ago

You can upgrade or remove __repr__, they are just for visualization

Domiinic Over a year ago

I'm upgrading. I just need to ajust the code because I simplifed my problem a lot to ask the question here. Shouldn't be too long ...

awesoon Over a year ago

Most likely you forgot to persons = Persons()

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