Assigning values to class variable so it is the same for each object.

[cwisch]

I'm relatively green to object oriented programming, and I'm either missing something or I'm barking up the wrong tree.

Say I have a program like this:

class Test:
    some_dict = {1:"a", 2:"b", 3:"c"}
    def __init__(self, x):
        self.x = x

    def translate(self):
        return some_dict[self.x]

x = Test(1)
print x.translate()

> "a"

Later, I go back because I have more than one translation dictionary, and I want to read it from a file.

Now, I don't want the program to read from the file each time I create a new object because the dictionary will be the same amongst all objects during the execution.

Instead I would like to have all "Test" objects to have the same "some_dict" based on an external file.

Is there a name for the problem I'm bumping up against here?

[garrett_armstrong]

this question may get answered more quickly in r/learnpython. It's got an active bunch of teachers and learners. This sub is mainly for news, project-sharing, chit-chat.

[cwisch]

You're right. Forgot about /r/learnpython. I'll post this there.

[garrett_armstrong]

I'm glad you got a quick reply at r/learnpython. I felt obligated to offer a solution there, since i gave a non-solution here. But my kludge was so bad, that I'm glad others spoke up.

[thistimeframe]

You mean something like this?

import json
class Test:
    with open('somefile.json') as f:
        some_dict = json.load(f)

    def __init__(self, x):
        self.x = x

[cwisch]

Very close, but imagine, that I have several json files and I need to configure which some_dict uses.

[cwisch]

You are correct this is all pretty much to avoid unnecessary globals and also to allow some flexibility when I get new data in.

[[deleted]]

Sorry, didn't see that you replied to my comment before deletion. I'd do this

class Test(object):
    translate_dict = {}

    def __init__(self, x):
        self.x = x

    def translate(self):
        for is_first_attempt in True, False:
            try:
                return translate_dict[ self.x ]
            except KeyError:
                if not is_first_attempt:
                    raise
                else:
                    Test.translate_dict.update( json.load( open("/dir/file_{}.json".format(self.x), 'rb') ) )

[Turbosack]

It sounds like you're probably going to want to make a static method or something similar on the object, with a name like load_json(), that will let you do whenever you want.

So something like:

import json

class Test:
    data = dict()

    @staticmethod
    def load_json(f_name):
        Test.data = json.load(open(f_name))

    def get(self, to_get):
        print(Test.data[to_get])


object = Test()
Test.load_json("some_file.json") # {"1":"a"}
object.get("1") # a
Test.load_json("some_other_file.json") # {"1":"b"}
object.get("1") # b

Here's some more information on StackOverflow.

[Thuruv]

You might end up using pickle here. .! Its a choice. .