Problem with Python class variables

# this is main.py Problem with python class variables
from Room import Room
from Character import Enemy, Friend, Character
from Item import Item
peter = Enemy("Peter", "smile")
sam = Enemy("sam","OK person")

print("enemies_defeated = " + str(Enemy.enemies_defeated))# is 0 the value it was initialised with
Enemy.enemies_defeated=Enemy.enemies_defeated+1
print("enemies_defeated = " + str(Enemy.enemies_defeated))# is 1 as we incremented
print("\nnow enemies_defeated will be reset by set method applied by sam")
sam.set_defeated(10)# sam resets it to 10
print("enemies_defeated = " + str(Enemy.enemies_defeated))# class variable reset to 10
print("sam defeated = " + str(sam.enemies_defeated))# so sam sees 10
print("peter defeated = " + str(peter.enemies_defeated))# and peter sees 10

print("\nnow reset by peter")
peter.set_defeated(5)
print("enemies_defeated = " + str(Enemy.enemies_defeated))# is 5
print(" sam defeated = " + str(sam.get_defeated()))# is 5, note the get method is imbeded in print
print(" peter defeated = " + str(peter.get_defeated()))#is 5

print("sam resets it  to 4")
sam.set_defeated(4)
print("enemies_defeated = " + str(Enemy.enemies_defeated))# is 4
print(" peter defeated = " + str(peter.get_defeated()))# is 4
print(" sam defeated = " + str(sam.get_defeated()))# is 4

sam.enemies_defeated = sam.enemies_defeated-1 #this code works

print("enemies_defeated = " + str(Enemy.enemies_defeated))#is 4,why has it not changed
print("sam " + str(sam.enemies_defeated))# this is 3, is it a new variabe or what ??????????????
print("peter " + str(peter.enemies_defeated))#this is 4,why has it not changed?

print("enemies_defeated = " + str(Enemy.enemies_defeated))# is 4
print("peter defeated = " + str(peter.get_defeated()))# is 4
print("sam defeated = " + str(sam.get_defeated()))# is 4
print("bye end of program")