Question

不使用继承，我们可以在一个类的两个实例之间共享一个变量吗？问题在于该变量需要3.5GB。使用继承不是一个好选择，因为我可能会也可能不会加载此变量。

Answer 1

您可以为此使用类变量。请看下面一个家庭共享一个帐户的简单示例。

https://www.tutorialspoint.com/python/python_classes_objects.htm

class FamilyAccount(object):
    total_amount = 0 # class variable

    def __init__(self, fullname, age):
        self.fullname = fullname # instance variable
        self.age = age           # instance variable

    def credit(self, amount):
        FamilyAccount.total_amount += amount

    def debit(self, amount):
        FamilyAccount.total_amount -= amount

    def details(self):
        print("Fullname: ", self.fullname)
        print("Age     : ", self.age)
        print("Amount  : ", self.total_amount)
        print() # new line

# Create account for Rishikesh Agrawani
account1 = FamilyAccount("Rishikesh Agrawani", 26)
# Rishikesh Agrawani credits 1000
account1.credit(1000)
# Print account information of Rishikesh Agrawani
account1.details() # 1000


# Create account for Shay Banon
account2 = FamilyAccount("Shay Banon", 30)
# Shay Banon debits 500
account2.debit(500)
# Print account information of Shay Banon
account2.details() # 500

# Print account information of Rishikesh Agrawani (again)
account1.details() # 500

# Fullname:  Rishikesh Agrawani
# Age     :  26
# Amount  :  1000

# Fullname:  Shay Banon
# Age     :  30
# Amount  :  500

# Fullname:  Rishikesh Agrawani
# Age     :  26
# Amount  :  500

如果您要使用10以外的其他值来初始化类变量，例如0，则可以如下修改上述代码。

class FamilyAccount(object):
    total_amount = 0 # class variable

    def __init__(self, fullname, age, amount = 0, set_amount = False):
        if set_amount: 
            # If you want to reset amount for all members
            # total_amount will be re-intialized (visible to all instances)
            FamilyAccount.total_amount = amount

        self.fullname = fullname # instance variable
        self.age = age           # instance variable

    def credit(self, amount):
        FamilyAccount.total_amount += amount

    def debit(self, amount):
        FamilyAccount.total_amount -= amount

    def details(self):
        print("Fullname: ", self.fullname)
        print("Age     : ", self.age)
        print("Amount  : ", self.total_amount)
        print() # new line

# Create account for Rishikesh Agrawani
account1 = FamilyAccount("Rishikesh Agrawani", 26, 10, set_amount = True)
# Rishikesh Agrawani credits 1000
account1.credit(1000)
# Print account information of Rishikesh Agrawani
account1.details() # 1010


# Create account for Shay Banon
account2 = FamilyAccount("Shay Banon", 30)
# Shay Banon debits 500
account2.debit(500)
# Print account information of Shay Banon
account2.details() # 510

# Print account information of Rishikesh Agrawani (again)
account1.details() # 510

# Fullname:  Rishikesh Agrawani
# Age     :  26
# Amount  :  1010

# Fullname:  Shay Banon
# Age     :  30
# Amount  :  510

# Fullname:  Rishikesh Agrawani
# Age     :  26
# Amount  :  510

在Python中的一个类的两个实例之间共享变量

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