How to Assign a dynamic value to MySQL @variable with python?

Question

i know my issue is simple but i could not find a solution anywhere, i need to assign a python variable to mysql @variable like this .

cur=db.cursor()
val =50
cur.execute('SET @var := (val)')
cur.execute('SELECT @var ;')
x=cur.fetchone()
cur.close()

i want to assign python a changing variable "val" to Mysql @var,