Question on how to call a function defined in a class in python

Question

I'm trying to understand how classes and self work. I now have the following code that has one class and functions defined in it.

from typing import Dict, Any


class LearnClasses:
    def checks(self) -> Dict[str, Any]:
        return {
            **self.chk1(),
            **self.chk2(),
            **self.chk3(),
        }

    def chk1(self) -> Dict[str, Any]:

        chk_id = self.chk1.__name__

        return {
            f'{chk_id}': "Is"
        }

    def chk2(self) -> Dict[str, Any]:

        chk_id = self.chk1.__name__

        return {
            f'{chk_id}': "it"
        }

    def chk3(self) -> Dict[str, Any]:

        chk_id = self.chk3.__name__

        return {
            f'{chk_id}': "working?"
        }

Could someone explain how to call the function checks in LearnClass?

I tried LearnClasses.checks() and it didn't work.

Blckknght · Accepted Answer · 2020-05-07 03:17:13Z

In general, to call normal methods in a class, you need to create an instance of the class. Then you call the method on the instance:

instance = LearnClasses()
instance.checks()

Note that the code you have now doesn't make a whole lot of sense. The usual purpose of a class is to store some data along side methods that operate on it. Your LearnClasses class doesn't have any data to store or operate on, so it's not very useful.

A slightly more illustrative example might be:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def info(self):
        return f"{self.name} is {self.age} years old"

You'd create the instance by calling the class, which invokes the __init__ method to store the data we have for the person. The info method does something useful with that data, producing a string:

joe = Person("Joe", 39)
print(joe.info())              # prints "Joe is 39 years old"

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