class Weapon():
    def __init__(self, health = 0, attack = 0, defense = 0, vampirism = 0,
                 heal_power = 0):
        self.health = health
        self.attack = attack
        self.defense = defense
        self.vampirism = vampirism
        self.heal_power = heal_power
class Sword(Weapon):
    def __init__(self):
        super().__init__(health = 5, attack = 2)
class Warrior:
    maxhealth = 50
    name = 'warrior'
    def __init__(self, health = 50, attack = 5, defense = 0):
        self.health = health
        self.attack = attack
        self.defense = defense
        self.equipped_list = []

 def equip_weapon(self, weapon):
        if not isinstance(weapon, Weapon()):
            weapon = Weapon()
        self.equipped_list.append(weapon) #пока пишем вручную
        self.health += weapon.health
        self.attack += weapon.attack
        self.............

 def equip_weapon(self, weapon):
        if not isinstance(weapon, Weapon):
            weapon = Weapon()
        list2 = [a for a in dir(weapon) if not a.startswith('__')]
        for a in list2:
            if self.a and self.a != 0:
                self.a += weapon.a
        self.equipped_list.append(weapon)

 Traceback (most recent call last):
  File "<pyshell#145>", line 1, in <module>
    a.equip_weapon(b)
  File "C:/Users/Леха/Desktop/Battle/another solution test.py", line 32, in equip_weapon
    if self.a and self.a != 0:
AttributeError: 'Warrior' object has no attribute 'a'

 if not isinstance(weapon, Weapon):
            weapon = weapon()

 for a in list2:
            if self.a and self.a != 0:
                self.a += weapon.a

 def equip_weapon(self, weapon):
        if not isinstance(weapon, Weapon):
            weapon = weapon()
        list1 = [getattr(weapon,a) for a in dir(weapon) if not a.startswith('__')]
        list2 = [a for a in dir(weapon) if not a.startswith('__')]
        list3 = dict(zip(list2, list1))
        for element in list3:
            if hasattr(self, element):
                setattr(self, element, getattr(self, element) + list3[element])
        self.equipped_list.append(weapon)

 And finally, you should add an equip_weapon(weapon_name) method to all of the soldiers classes. It should equip the chosen soldier with the chosen weapon.
This method also should work for the units in the army. You should hold them in the list and use it like this:
my_army.units[0].equip_weapon(Sword()) - equip the first soldier with the sword.

 class Weapon():
    def __init__(self, health = 0, attack = 0, defense = 0, vampirism = 0,
                 heal_power = 0):
        self.health = health
        self.attack = attack
        self.defense = defense
        self.vampirism = vampirism
        self.heal_power = heal_power
class Sword(Weapon):
    def __init__(self):
        super().__init__(health = 5, attack = 2)
class Warrior:
    maxhealth = 50
    name = 'warrior'
    def __init__(self, health = 50, attack = 5, defense = 0):
        self.health = health
        self.attack = attack
        self.defense = defense
        self.equipped_list = []
    def equip_weapon(self, weapon:Weapon):
        self.equipped_list.append(weapon)
        self.health += weapon.health
        self.attack += weapon.attack
        self.defense += weapon.defense
#
#
my_warrior = Warrior()
print('было:')
print(my_warrior.health, my_warrior.attack, my_warrior.defense)
my_warrior.equip_weapon(Sword())
print('стало:')
print(my_warrior.health, my_warrior.attack, my_warrior.defense)
print(my_warrior.equipped_list)

 было:
50 5 0
стало:
55 7 0
[<__main__.Sword object at 0x00000253005DEA48>]
Process finished with exit code 0

 self.health *= weapon.health
self.attack -= weapon.attack
self.defense += weapon.defense

 class Warrior:
    maxhealth = 50
    name = 'warrior'
    def __init__(self, health = 50, attack = 5, defense = 0):
        self.health = health
        self.attack = attack
        self.defense = defense
        self.equipped_list = []
    @property
    def is_alive(self):
        return self.health > 0
    @property
    def god_heal (self):
        self.health = self.maxhealth
    def hit(self, other):
        other.health -= other.damage(self.attack)
    def damage(self, attack):
        return max(attack - self.defense, 0)
    def equip_weapon(self, weapon):
        if not isinstance(weapon, Weapon):
            weapon = weapon()
        list1 = [getattr(weapon,a) for a in dir(weapon) if not a.startswith('__')]
        list2 = [a for a in dir(weapon) if not a.startswith('__')]
        list3 = dict(zip(list2, list1))
        for element in list3:
            if hasattr(self, element) and getattr(self,element) != 0:
                setattr(self, element, getattr(self, element) + list3[element])
        self.equipped_list.append(weapon)
    def equip_weapon2(self,weapon):
        self.equipped_list.append(weapon)
        self.health += weapon.health
        self.attack += weapon.attack
        self.defense += weapon.defense
        self.vampirism += weapon.vampirism
        self.heal_power += weapon.heal_power
class Vampire(Warrior):
    maxhealth = 40
    name = 'vampire'
    def __init__(self):
        super().__init__(health = 40, attack = 4)
        self.vampirism = 50
        
    def hit(self,other):
        other.health -= other.damage(self.attack)
        self.health = min(self.health + math.floor(self.vampirism
                          / 100 * other.damage(self.attack)), self.maxhealth)
class Weapon():
    def __init__(self, health = 0, attack = 0, defense = 0, vampirism = 0,
                 heal_power = 0):
        self.maxhealth = health
        self.health = health
        self.attack = attack
        self.defense = defense
        self.vampirism = vampirism
        self.heal_power = heal_power
class Catana(Weapon):
    def __init__(self):
        super().__init__(health = -20, attack = 6, defense = -5, vampirism = 50)