python import csv to sqlite

Hi i am trying to import a csv file to a sqlite3 database using python tkinter. I open file using askopenfilename dialog and pass the file to readFile function.

def csvFile(self):
        f1 = askopenfilename()
       self.readFile(f1)

def readFile(self, filename):
    conn = sqlite3.connect('Unicommerce.db')
    cur = conn.cursor() 
    cur.execute("""CREATE TABLE IF NOT EXISTS unicom(products varchar,channel varchar,regulatory_forms varchar,shipment varchar)""")
    filename.encode('utf-8')
    print "test1"
    reader = csv.reader(filename)
    for field in reader:
        cur.execute("INSERT INTO unicom VALUES (?,?,?,?);", field)

    conn.commit()
    conn.close()

I am getting this error.

cur.execute("INSERT INTO unicom VALUES (?,?,?,?);", field)
ProgrammingError: Incorrect number of bindings supplied. The current statement uses 4, and there are 1 supplied.

I tried every possoible solution available but couldn't import file to database.
I also tried tried solutions given in these links
Importing a CSV file into a sqlite3 database table using Python
Python CSV to SQLite