Accessing Variables and Methods Outside of Class Definitions

Access class method variable outside of class

Yes there is, your existing code assigns 'something' to x, but this x is actually not associated with the class instance. Change x = 'something' to self.x = 'something' does the trick.

class Person:
    def do_something(self):
        self.x = 'something'

person = Person()
person.do_something()

print(person.x)
# Prints 'something'

Refer to this answer if you want to know more about the subtleties of initializing class variables.

Accessing variable inside class from outside function in python

Updating values by passing the list as an argument:

class A:
   def insideclass(self):
       values=[]
       for i in range(10):
           func(values)

def func(values):
    now = datetime.time.now()
    if now == "2021-06-25 10:15:52.889564":
        # You can't compare a datetime to a string...
        values.clear()
    values.append(now)

You could throw an exception if the condition is met and perform the clear in the class method

class A:
   def insideclass(self):
       values=[]
       for i in range(10):
           try:
               values.append(func())
           except:
               values.clear()

def func():
    now = datetime.time.now()
    if now == "2021-06-25 10:15:52.889564":
        raise Exception('This should be a more specific error')
    else:
        return now

How to access a Variable or list or dictionary inside a method of a class, outside the class?

Like this:

class test:
    def __init__(self):
        self.ar = []
        self.dict_t = {}
        self.a = 0
        print('inside the code')

    def add(self, x, y):
        self.a = x+y

    def list_test(self):
        self.ar.append(1)
        self.ar.append(2)

    def dict_test(self):
        self.dict_t = {1: 2, 2: 3}

t = test()
t.list_test()
print(t.ar)
t.add()
print(t.a)

Note:

Define your variables in the initiate function.
Then you can access them through:

class_name.var_name

Accessing class variables outside the class in python

First you need to create an instance of the class, then you can use that instance to access its instance variable and function.

Below is a simple example based on your code

import tkinter as tk

class First:
    def __init__(self, root):
        self.root = root
        self.root.title('First window')
        self.root.geometry('1350x700+0+0')
        
        self.mystring = tk.StringVar(self.root)

        self.txt_id = tk.Entry(self.root, textvariable=self.mystring, font=("Times New Roman", 14), bg='white')
        self.txt_id.place(x=200, y=400, width=280)

        btn_search = tk.Button(self.root, text="Show in class", command=self.get_id)
        btn_search.place(x=100, y=150, width=220, height=35)

    def get_id(self):
        val = self.mystring.get()
        print("inside class:", val)
        return val

root = tk.Tk()

# create an instance of First class
app = First(root)

def show():
    # get the text from the Entry widget
    print("outside class:", app.get_id())

tk.Button(root, text="Show outside class", command=show).pack()

root.mainloop()

Note that I have change class name from first to First because it is normal practise.

How to access variables of a method in a different class in Java?

In Java, variables declared inside a method have a scope limited to the method : they are not accessible outside of the method, even in the same class.

In that case, if you want to access them from outside, this means that their place is probably not as variables of the method, but as members of the class, ie "variables" declared as properties of the class, like this :

class Example {

   public int field; 

}

If you are referring to members, then whether you can access this field from outside the class depends on what you write in front of the field declaration :

public : field will be accessible outside of the class
protected : field will be accessible only in classes that extend this class
private : field will be accessible only inside that class

C++ Class - using public variables and defining member functions outside class

For 1., If f is not declared in the class C (that is, in C.h), you cannot. you cannot add a function to a class dynamically.

Also if is is declared in C.h and also defined in C.cpp, then you are attempting to duplicate its definition, you cannot as well.

If it is declared in C.h and not defined in C.cpp, you can define it here in the main's file, BUT this is not recommended (bad practice). Better put all the class's definitions of methods in its .cpp file.

For 2, You can modify an attribute for an object of class C if that member was declared in the public section of the class:

class C {
... // private members
public: // public section
    double x;
    ... // other public members, methods or attributes
};

In this case you can, in main:

C P;
P.x = 5.67;

Access a variable inside a class from outside the class

For this scenario you can use Object properties,

Define a public variable inside your class,

class Test(){

    public $b;

    function fun(){
        $a= 0;
        $this->b = 5;
        $sum = $this->b+c;
        return $sum;
    }
}

$obj = new Test();
$b = $obj->b; // here null
echo $obj->fun();
$b = $obj->b; // here 5