How to solve can't adapt type 'Series' in psycopg2

Question

I want to insert a record with psycopg2. The code is simple:

import psycopg2
query = """
    INSERT INTO xxx (lon,lat)
    VALUES(%s,%s)"""
cursor.execute(query, (df2['lon'],df2['lat']))
 conn.commit()
cursor.close()
conn.close()

However the code does not work and raised the below error:

psycopg2.ProgrammingError: can't adapt type 'Series'

How do I solve the issue?