CODEWITHSUNDEEP
pythonpython-3.xclass
DS3a
DS3a

Reputation: 131

Identifying instances based on unique attributes in python

I'm working on a project and it would make it easier for me to code if we can identify class attributes based on their unique instances. example

class MyClass:
    def __init__(self, unique_id):
        self.unique_id = unique_id

and later

class1 = MyClass(1)
class2 = MyClass(2)

Is it possible to do get the object class1 as an output if

output = instance whose unique_id == 1

Upvotes: 0

Views: 99

Answers (2)

Rohi
Rohi

Reputation: 814

Option A :

If you are planing on adding the id's in a consecutive way you could enter them all into a list :

class_list = []
class_list.append(MyClass(1))
class_list.append(MyClass(2))

And then get them using

class_list[index]

Option B :

If you arent going to them consecutively you could do the following

class_dict = {}
class_dict{"some_id"} = MyClass("some_id")
class_dict{"some_id2"} = MyClass("some_id2")

and then access as following :

class_dict["some_id"]

Option C - Prefered:

Personally I would recommend the following :

class MyClass:
    static_dict = {}
    def __init__(self, unique_id):
        self.unique_id = unique_id
        MyClass.static_dict[unique_id] = self

    def get_class_by_id(unique_id):
        return static_dict[unique_id]

and then you could access as following:

MyClass.get_class_by_id("some_id")

Upvotes: 1

Thierry Lathuille
Thierry Lathuille

Reputation: 24232

You can keep a dict of instances: 

class MyClass:
    _instances = {}

    def __init__(self, unique_id):
        self.unique_id = unique_id
        self._instances[unique_id] = self

    @classmethod
    def instance_by_id(cls, id):
        return cls._instances[id]


a = MyClass(1)
b = MyClass(2)


c = MyClass.instance_by_id(1)

print(c)
print(a)
#<__main__.MyClass object at 0x7fa9dd0bfbe0> 
#<__main__.MyClass object at 0x7fa9dd0bfbe0>

Upvotes: 1

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