I am new at writing production code, and I want inspiration on how to use variables when I write classes. I use Python here but this can be generilzed to other languages. What is good programming practice? Declaring in the same document or do it in a seperate.

import pandas as pd

someValue = 'Variable value'
data_col1 = 'col1'

class MyClass:
    def __init__(self, data: pd.DataFrame):
        self.variable1 = someValue
        self.variable2 = data[data_col1].max()

Alternatively have another document with declaring the variables and do this:

import pandas as pd
import variables as var

class MyClass:
    def __init__(self, myData: pd.DataFrame):
        self.variable1 = var.someValue
        self.variable2 = myData[var.data_col1].max()

How would you structure this. number 1, number 2 or something entirely different?