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 3、类型的可变与不可变

int float bool str list tuple dict

不可变类型: int float bool str tuple

可变类型: list dict

num = 10

num = 20

my_list = [1, 2]

my_list.append(3)

a = 1000
b = 1000
print(id(a), id(b)) # python中的内存优化,对于不可变类型进行的,
print(id(a) == id(b))

a = 'hello'
b = 'hello'
print(id(a), id(b)) # python中的内存优化,对于不可变类型进行的,

my_tuple = (1, 2)
my_tuple1 = (1, 2)
print(id(my_tuple), id(my_tuple1))
print(id(my_tuple) == id(my_tuple1))
print('-' * 20)
my_list = [1, 2, 3]
my_list1 = [1, 2, 3]
print(id(my_list), id(my_list1))

print('' 30)
my_tuple2 = (1, 2, [3, 4])
print(my_tuple2)
my_tuple22 = 10
print(my_tuple2)

4、引用作为函数参数传递
关系到到底要不要在函数中添加global 

函数传参传递的也是引用

my_list = [1, 2, 3] # 全局变量

def func1(a):

a.append(4)

def func2():

# 为啥不加global, 因为没有修改 my_list 中存的引用值
my_list.append(5)

def func3():

global my_list
my_list = [1, 2, 3]   # 修改全局变量的值

def func4(a):

# += 对于列表来说,类似列表的extend方法,不会改变变量的引用地址
a += a  # a = a + a, 修改了a变量a的引用
# print(a)

func1(my_list) # [1, 2, 3, 4]
func2() # [1, 2, 3, 4, 5]
func3() # [1, 2, 3]
print(my_list)

b = 10 # 不可变类型
func4(b)
print(b) #

func4(my_list)
print(my_list) # [1, 2, 3, 1, 2, 3]