import pymysql
import traceback

cnx = pymysql.connect(host='localhost', port=3306,
					user='root', password='', database='db',
					  charset='utf8mb4',
                      cursorclass=pymysql.cursors.DictCursor)

with cnx.cursor() as cursor:
	try:
		cursor.execute("SELECT * FROM some_table")
		d = cursor.fetchall()
		for item in d:
			print(item)
	except:
		print(traceback.format_exc())
		cnx.rollback()

cnx.commit()
cnx.close()