python基础之数据内存相关

数据内存相关

 

示例-：
v1 = [11,22,33]
v2 = [11,22,33]
v1 = 666
 v2 = 666
v1 = "asdf"
v2 = "asdf"

# 按理 v1 和 v2 应该是不同的内存地址。特殊：
1. 整型：  -5 ~ 256 （id一样）
2. 字符串：（常见字符串）"alex",'asfasd asdf asdf d_asdf '      （包含特殊字符）"f_*" * 3（或者相乘大于3） 还有列表 - 重新开辟内存。

示例二：

v1 = [11,22,33,44]  （v1重新赋值后，旧的值将被解析器当成垃圾清理掉）
v1 = [11,22,33]

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[11, 22, 33]

示例三：

v1 = [11,22,33]
v2 = v1

# 练习1 (内部修改)
v1 = [11,22,33]
v2 = v1
v1.append(666)
print(v2) # 含 666

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[11, 22, 33, 666]

 

# 练习2：（赋值）
v1 = [11,22,33]
v2 = v1
v1 = [1,2,3,4]
print(v2)

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[11, 22, 33]

 

 

# 练习3：(重新赋值)
#重新赋值
v1 = 'sundy'
v2 = v1
v1 = 'amy'
print(v2)

D:python3.6python3.6.exe D:/python_code/day01/day06.py
sundy

#示例四：

v = [1,2,3]
values = [11,22,v]
练习1：
 
 v.append(9)
 print(values)

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[11, 22, [1, 2, 3, 9]]

 
 
 
 练习2
v = [1,2,3]
values = [11,22,v]
values[2].append(66)
print(values)

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[11, 22, [1, 2, 3, 66]]

 

 练习3：
v = [1,2,3]
values = [11,22,v]
v = 999
print(values)
 
 D:python3.6python3.6.exe D:/python_code/day01/day06.py
[11, 22, [1, 2, 3]]

 练习4：
v = [1,2,3]
values = [11,22,v]
v = 999
values[2] = 666
print(v)

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[1, 2, 3]

查看内存地址

v1 = [1,2,3]
v2 = v1
v1.append(999)
print(v1,v2)
print(id(v1),id(v2))

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[1, 2, 3, 999] [1, 2, 3, 999]
1188414396872 1188414396872

 

v1 = [1,2,3]
v2 = v1
print(id(v1),id(v2))
v1 = 999
print(id(v1),id(v2))

D:python3.6python3.6.exe D:/python_code/day01/day06.py
2339259718088 2339259718088
2339258862448 2339259718088

问题： == 和 is有什么区别？
 == 用于比较值是否相等。
 is 用于比较内存地址是否相等
 
 
 
 a = [[1,2,3],[4,5,6]]
b = []
for i in a:
    print(i)
    b.append(i)
print(id(a),id(b))
print(id(a[1]),id(b[1]))

 

D:python3.6python3.6.exe D:/python_code/day01/day06.py
[1, 2, 3]
[4, 5, 6]
2591750527496 2591749628168
2591750527304 2591750527304