图解Python中深浅copy（通俗易懂）

拼搏现实的明天。 2023-07-09 02:08 5阅读 0赞

#### 一、深浅copy ####

1.  赋值运算

l1 = [1, 2, 3, [22, 33]]
    l2 = l1
    l1.append(666)
    
    print(l1)  # [1, 2, 3, [22, 33], 666]
    print(l2)  # [1, 2, 3, [22, 33], 666]

**图解：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbGxfbHVjeQ_size_16_color_FFFFFF_t_70]

**注意：`l2 = l1`是一个指向，是赋值，和深浅copy无关。**

1.  浅copy

**其实列表是一个一个的槽位，每个槽位存储的是该对象的内存地址**

例1. 给大列表添加元素
    l1 = [1, 2, 3, [22, 33]]
    l2 = l1.copy()
    # 或者下面这种方式，也是浅copy
    # import copy
    # l2 = copy.copy(l1)
    l1.append(666)
    
    print(l1)  # [1, 2, 3, [22, 33], 666]
    print(l2)  # [1, 2, 3, [22, 33]]
    
    例2. 给小列表添加元素
    l1 = [1, 2, 3, [22, 33]]
    l2 = l1.copy()
    l1[-1].append(666)
    
    print(l1)  # [1, 2, 3, [22, 33, 666]]
    print(l2)  # [1, 2, 3, [22, 33, 666]]、
    
    例3. 将l1列表中第一个元素改为6
    l1 = [1, 2, 3, [22, 33]]
    l2 = l1.copy()
    l1[0] = 6
    
    print(l1)  # [6, 2, 3, [22, 33]]
    print(l2)  # [1, 2, 3, [22, 33]]

**图解：**

例1

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbGxfbHVjeQ_size_16_color_FFFFFF_t_70 1]

例2

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbGxfbHVjeQ_size_16_color_FFFFFF_t_70 2]

例3

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbGxfbHVjeQ_size_16_color_FFFFFF_t_70 3]

**总结：**

浅copy：会在内存中新开辟一个空间，存放这个copy的列表，但是列表里面的内容还是沿用之前对象的内存地址。

**注意：**

切片中，如果是全切，属于浅copy。

1.  深copy

import copy
    l1 = [1, 2, 3, [22, 33]]
    l2 = copy.deepcopy(l1)
    l1.append(666)
    print(l1)  # [1, 2, 3, [22, 33], 666]
    print(l2)  # [1, 2, 3, [22, 33]]

**图解：**

本质如下图：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbGxfbHVjeQ_size_16_color_FFFFFF_t_70 4]

但是python对深copy做了一个优化，将可变的数据类型在内存中重新创建一份，而不可变的数据类型则沿用之前的，所以内存中是下面这样的：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbGxfbHVjeQ_size_16_color_FFFFFF_t_70 5]

**总结：**

深copy：会在内存中开辟新空间，将原列表以及列表里面的可变数据类型重新创建一份，不可变数据类型则沿用之前的。

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