import pyodbc
import pandas as pd
...
cnxn = pyodbc.connect('DRIVER={{Microsoft Access Driver (*.mdb, *.accdb)}};DBQ=' + \
                      '{};Uid={};Pwd={};'.format(db_file, user, password)

query = "SELECT * FROM mytable WHERE INST = '796116'"
dataf = pd.read_sql(query, cnxn)
cnxn.close()