feeding

i have been feeding my ball python rats for the last few months then all of a sudden he stop eating rats he stop eating for a month so i go and buy a mice today and he eats it is this normal for him not to eat the rat

Sounds typical for a ball python. If your husbandry is good I wouldn't worry about going off feed for just a month...

Is not out of the ordinary that ball pythons go off feeding, some may eat another meal for many months to come. Also some ball pythons stop feeding on rats & now prefer mice or vice versa.