correct syntax for SQL calls in python with pyodbc

I need help to write the SQL calls from my python scripts in a proper way. what I my script currently looks like is :

import pyodbc
cnx = pyodbc.connect(**connection details**)
c = cnx.cursor()
results = c.execute("select * .....")
final_result= results.fetchall()

issue is sometimes result value is NONE type object and sometimes I get a return values.

I want to know if the below way is a correct way to call , because it seems to work everytime for all the queries

import pyodbc

cnx = pyodbc.connect(**connection details**)

c = cnx.cursor()

c.execute("select * .....")
final_result= c.fetchall()