Use a variable with a call to a module function

Question

I am not sure I phrased my question exactly right, but here is the code to illustrate:

script.py
from simple_salesforce import Salesforce
sf = Salesforce(login stuff here)
with open(nextObjFile, 'r') as f :
    nextObj = f.read().strip()

simple salesforce has a sf..describe() that I need to pass nextObj into. Is this possible? I tried sf.nextObj.describe() and that does not work.