Importing a class with its dependencies

I am trying to import a class I have created from another file, into my current working file. The class is as follows in this example:

ClassFile

class example_class:
    
    def __init__(self, ticker):
        self.df = yf.download(ticker, start='2020-12-31')
    
    def do_something(self):
        return something

Then when I go to import it into my working file, and run the code:

WorkingFile

import ClassFile
import yfinance as yf

instance = example_class('MSFT')

I get the following error:

name 'yf' is not defined

I understand that yfinance is not being imported somewhere but, after researching, I have not been able to understand how to import it.

Essentially, I am trying to understand how to import a class from another file alongside the dependencies within said class.

You either specifically import the class if you want to use its name without the file classifier (ClassFile) or use the Classifier with the function name. You do NOT have to import the depenency modules. ie

import ClassFile

instance = ClassFile.example_class('MSFT')

or:

from ClassFile import example_class

instance = example_class('MSFT')

I assume yf is imported or declared somehwere in ClassFile. That is put you r yf import statement in ClassFile

You need to import the symbol where you use it; in ClassFile.

import yahoofinance as yf

class example_class:
    
    def __init__(self, ticker):
        self.df = yf.download(ticker, start='2020-12-31')
    
    def do_something(self):
        return something

When you import something, it is imported into the current scope, i.e. the current file of code.

In theory, if you left import ... yf in WorkingFile.py, you could say

import WorkingFile

...
    self.df = WorkingFile.yf.download(ticker, start='2020-12-31')

though of course in this case, that would create a circular import; and anyway, you don't want to do this - it is completely insane. The entire job of import is to bring in something where you actually need it.

The other way around is how you are supposed to use it; the user of ClassFile should not need to know or care that the implementation uses yfinance internally. A proper class should encapsulate its internals from its users, and only expose functionality that they directly need.

In some scenarios, you need to compromise; for example, if ClassFile is a really thin wrapper around yfinance (let's say it inherits from it and adds a new method sell_MSFT but otherwise works identically) then of course the user needs to be familiar with yfinance anyway, and you can defer to its documentation for most of the functionality. But still, in that case, the import yfinance needs to go where it is actually used; in ClassFile.