Execute Method within Class Python

Question

I'm trying to call a method within a class MyClass and have its value returned.

class MyClass:
    def __init__(self):
        print " Class Initialized"

    def gather_path(self):
        self.tld_object = Tld.objects.get(id=3,FKToClient=User.pk)
        return self.tld_object

How do I return the value of self.tld_object by importing my class in Python intrepreter.

I'm importing like:

from MyApp.MyClass import gather_path()

I know, this is quite basic - I'm relatively new to OOP in Python.

how do I then call this method to return the value of return self.tld_object within gather_path() method?

Why do you have a class at all? why not make gather_path a module level function? — mgilson
– mgilson, Commented May 22, 2014 at 19:11
There are other methods like gather_<whatever> in the class , I'm specifically trying to use the return value from gather_path() — CodeTalk
– CodeTalk, Commented May 22, 2014 at 19:12
Wouldn't from MyApp.MyClass import gather_path() be invalid syntax? — 2rs2ts
– 2rs2ts, Commented May 22, 2014 at 19:18
Just follow and finish one of the recommended Python OOP courses. Unless you keep on asking questions on syntactic non-sense. — Sascha Gottfried
– Sascha Gottfried, Commented May 22, 2014 at 19:18

Community · Accepted Answer · 2017-05-23 10:26:18Z

4

It depends on what you're trying to do, but typically, I think the code importing your class would look like this:

from MyApp import MyClass

my_instance = MyClass()
value = my_instance.gather_path()

The value variable will now contain tld_object's value.

If you don't want to instantiate MyClass in order to call get_path(), you need to make get_path() either a class or static method.

From your example, it's not clear that you need to set self.tld_object, since you're just returning it from gather_path() anyway, unless other methods are relying on that state under the hood. If you are, though, it would be better practice to declare it in __init__, even if you set it to None. Alternatively, if all instances of MyClass are going to use the same value of tld_object, you could make it a class variable, and just declare it outside of any method, like so:

class MyClass:
    tld_object = Tld.objects.get(id=3,FKToClient=User.pk)

    def gather_path(self):
        return self.tld_object

Not sure how much of that is relevant to your needs, it's a bit hard to tell from the given example. If I were writing this (given what you've said so far), I'd do the following:

class MyClass:
    def __init__(self):
        self.tld_object = Tld.objects.get(id=3,FKToClient=User.pk)
        # Maybe raise an exception or something if self.tld_object doesn't get set right

    # Example of how to access tld_object from another method
    def print_tld_object(self):
        print self.tld_object

If you need to reach tld_object from outside the class, you would do the following in the other module:

from MyApp import MyClass

my_instance = MyClass()
tld = my_instance.tld_object

edited May 23, 2017 at 10:26

CommunityBot

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answered May 22, 2014 at 19:15

Nacho

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9 Comments

CodeTalk Over a year ago

How will this possibly return a value though? Wouldn't I need "return value" at the end ?

Nacho Over a year ago

Well, you would access my_instance.tld_object after calling gather_path(), though depending on your needs, that might not be what you want.

CodeTalk Over a year ago

What I'm trying to do is use the value of self.tld_object within another method named newmethod that will use the value of self.tld_object. what is best practice for that? I really appreciate the answer

Nacho Over a year ago

So, in your example, when you call self.tld_object = Tld.objects.get(id=3,FKToClient=User.pk), that makes it available to all other methods on that instance of MyClass. So other methods can just reference self.tld_object, assuming gather_path() was called beforehand. You should strongly consider moving the self.tld_object = Tld.objects.get(id=3,FKToClient=User.pk) line to your init method, or at least calling self.tld_object = None from init.

CodeTalk Over a year ago

Is it bad for performance to have multiple methods to just do a simple query - kinda how self.tld_object is doing? Is it better to put these statements just all in the init method?

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