python learning diary

1. Numeric copy

import copy
# ######数字、字符串######
n1 = 123
print(id(n1))
n2 = n1
print(id(n2))

###浅拷贝###
n2 = copy.copy(n1)
print(id(n2))

###深拷贝###
n3 = copy.deepcopy(n1)
print(id(n3))

C:\Users\811314\AppData\Local\Programs\Python\Python35-32\python.exe C:/homework/day3/1.py
492322480
492322480
492322480
492322480

Process finished with exit code 0

2, string

import copy
# ######数字、字符串######
n1 = "my name is hellworld"
print(id(n1))
n2 = n1
print(id(n2))

###浅拷贝###
n2 = copy.copy(n1)
print(id(n2))

###深拷贝###
n3 = copy.deepcopy(n1)
print(id(n3))

C:\Users\811314\AppData\ Local\Programs\Python\Python35-32\python.exe C:/homework/day3/1.py
5973920
5973920
5973920
5973920

Process finished with exit code 0

import copy
# ######数字、字符串######
n1 = ["helloworld","hapen"]
print(id(n1))
n2 = n1
print(id(n2))

###浅拷贝###
n2 = copy.copy(n1)
print(id(n2))

###深拷贝###
n3 = copy.deepcopy(n1)
print(id(n3))

C:\Users\811314\AppData\Local\Programs\Python\Python35-32\python.exe C:/homework/day3/1.py
12817912
12817912
10370784
12816672

Process finished with exit code 0

For numbers and strings, assignment, shallow copy and deep copy are meaningless because they always point to the same memory address .

Shallow copy, only create the first layer of data in the memory

Deep copy, recreate all the data in the memory copies (excluding the last layer, that is: Python's internal optimization of strings and numbers

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