Importing vars from another file

[vulturas]

Hello everyone :)
While doing my homework I came across the following problem:

We have to develop a GUI with PyQt - this task was not a problem.

The variables come from the QLineEdit and are always the same. Our professor wants us to write
a file named 'vars.py' and import the file into our 'main.py' - now I'm in trouble

Generally it wasn't a problem to import and use vars in other tasks before. But since the vars are coming from the GUI,
I don't know how to handle it. Using the (quoted) variables inside the main.py works perfectly.

I have tried this solution:

main.py

from vars import Incoming
# more code

def ShowStock(self):   
        """sep = "-"
        vendor = self.inhersteller.text().upper()
        size = self.ingr.text().upper()
        quant = self.inanz.text()          
        extension = ".hand"
        directory = "base"
        filename = vendor + "." + size + extension
        savefolder = os.path.join(directory, filename)
        """
        Incoming(self)
        
        if not vendor or not size:
            Empty()
        else:        
            if not os.path.isfile(savefolder):
                NoFile()
            else:
                # much more code

vars.py

def Incoming(self):
        sep = "-"
        vendor = self.inhersteller.text().upper()
        size = self.ingr.text().upper()
        quant = self.inanz.text()          
        extension = ".hand"
        directory = "base"
        filename = vendor + "." + size + extension
        savefolder = os.path.join(directory, filename)  

Error message is: builtins.NameError: name 'vendor' is not defined

Hope you can understand where the problem is.
Thank you very much in advance :)