Python的传值和传址

# 可变  
def func(x):  
    print(x) # [1, 2, 3]  
    x[0] = 100  
    return x  
y = [1,2,3]  
func(y)  
print(y) # [100, 2, 3]  

# 不可变  
def func(x,y):  
    x = x + 1  
    y = y - 3  
    return (x,y)      
a = 1  
b = 10  
func(a,b)  
print('x+y:',func(a,b)) # x+y: (2, 7)  
print('a:',a)                       # a: 1  
print('b:',b)                       # b: 10  

a=1  
def f(b):   
    b=2  
    return b  
f(a)  
print a  

# a是不可变的数字  
a = 1  
b = a  
a = 2  
print(a,b) # 2,1  
print(a is b) # False  

# a是可变的列表  
a = [1,2,3]  
b = a  
a[0] = 100  
print(a,b) # [100, 2, 3] [100, 2, 3]  
print(a is b) # True  

# 不可变数据类型  
a = 'hello'  
b = 'hello'  
print(a == b) # True  
print(a is b) # True  

# 可变数据类型  
x = y = [1,2,3]  
z = [1,2,3]  
print(x == y) # True  
print(x is y) # True  
print(x == z) # True  
print(x is z) # False  
print(y == z) # True  
print(y is z) # False  
print('x的id：',id(x))  
print('y的id：',id(y))  
print('z的id：',id(z))  
# x的id： 140392781111176  
# y的id： 140392781111176  
# z的id： 140392781111240