I am trying to create a multi-file environment for my project. The File structure is as such

project_folder
   |- FileA.py
   |- FileB.py

The FileA.py has mainly the script in it and also I have improted FileB here
FileA.py

import os,sys
from FileB import temp_class as T

// lines of code 
str = "somestring"
A, B, C = T.func(str)

// lines of code

FileB.py

import os,sys

class temp_class:
    def func(self, S):
        //lines of code
        return (someA,someB,someC)

But I am getting the error as

TypeError: unbound method func() must be called with temp_class instance as first argument (got str instance instead)

>Solution :

You just need to instantiate it: T_inst = T(), and then use T_inst.func().

To expand: the error message tells you that it expects to find an instance of T (temp_class) as its first argument. When you call a method of a class instance, that very instance is passed as the first argument (usually called "self"). In this case you tried to invoke it as a method of the class itself (like a static method) so this doesn’t happen, and self instead was assigned the string that you passed (with the second argument getting None instead of a string).

If you don’t want to instantiate the class then you could either declare func a static method (or in the docs here) of temp_class, or simply make temp_class a module instead of a class (i.e, define its "methods" outside of any class, with the hierarchical structure provided by the way you structure your modules; in your case, to obtain behavior identical to that which you seem to be going for: a directory called FileB that contains a __init__.py file (to make it function as a module) and a temp_class.py file with the function func defined within it).