Python学习——浅拷贝、深拷贝

骑猪看日落 2021-05-11 20:35 506阅读 0赞

##### 浅拷贝 #####

拷贝了引用，并没有拷贝内容

>>> a = [1,2]
    >>> b = a
    >>> id(a)
    1908594926216
    >>> id(b)
    1908594926216
    >>> # 以上 a b 只指向的地址为同一个地址，说明给同一变量赋值时 是复制的引用并赋值
    
    >>> c = { "name":"jack"}
    >>> d = c
    >>> id(c)
    1908594885760
    >>> id(d)
    1908594885760
    >>> c["age"] = 18
    >>> c
    { 'name': 'jack', 'age': 18}
    >>> d
    { 'name': 'jack', 'age': 18}
    >>>  # 因为是地址的拷贝， 所以通过c引用修改值，则d引用看到的值也发生了变化

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70]

##### 深拷贝 #####

是对一个对象的所有层次的拷贝  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 1]  
进一步理解深拷贝  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 2]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 3]

##### 拷贝的其它方式 #####

分片表达式可以赋值一个序列  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 4]  
字典的copy方法可以拷贝一个字典  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 5]

##### 注意点 #####

浅拷贝对不可变类型和可变类型的copy不同  
1.copy.copy对于可变类型，会进行浅拷贝  
2.copy.copy对于不可变类型，不会拷贝，仅仅是指向

In [88]: a = [11,22,33]
    In [89]: b = copy.copy(a)
    In [90]: id(a)
    Out[90]: 59275144
    In [91]: id(b)
    Out[91]: 59525600
    In [92]: a.append(44)
    In [93]: a
    Out[93]: [11, 22, 33, 44]
    In [94]: b
    Out[95]: [11, 22, 33]
    In [96]: id(a[0])
    Out[97]: 59273406
    In [98]: id(b[0])
    Out[99]: 59273406
    
    In [100]: a = (11,22,33)
    In [101]: b = copy.copy(a)
    In [102]: id(a)
    Out[103]: 58890680
    In [104]: id(b)
    Out[105]: 58890680

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 6]

##### copy.copy和copy.deepcopy的区别 #####

copy.copy  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 7]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 8]  
copy.deepcopy  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 9]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxNDgyNTk5_size_16_color_FFFFFF_t_70 10]  
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