update 03-notes

Author: linearalgebrayhz

03-dict-set/03-notes.ipynb

@@ -286,8 +286,149 @@
     "\n",
     "这一切的背后其实都靠的是`__missing__`方法。\n",
     "\n",
-    "### 3.4.2 `__missing__`方法\n"
+    "### 3.4.2 `__missing__`方法\n",
+    "\n",
+    "\n",
+    "## 3.7 不可变的映射类型 `types.MappingProxyType`\n",
+    "> 如果给这个类一个映射，它会返回一个只读的映射视图。虽然是个只读视图，但是它是动态的。也就是说，如果对原映射做出了改动，我们通过这个视图可以观察到，但是无法通过这个视图对原映射做出改动。"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "mappingproxy({1: 'A'})"
+      ]
+     },
+     "execution_count": 1,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "from types import MappingProxyType\n",
+    "d = {1:\"A\"}\n",
+    "d_proxy = MappingProxyType(d)\n",
+    "d_proxy"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'A'"
+      ]
+     },
+     "execution_count": 2,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "d_proxy[1]"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "TypeError",
+     "evalue": "'mappingproxy' object does not support item assignment",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[1;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
+      "Cell \u001b[1;32mIn[3], line 1\u001b[0m\n\u001b[1;32m----> 1\u001b[0m \u001b[43md_proxy\u001b[49m\u001b[43m[\u001b[49m\u001b[38;5;241;43m2\u001b[39;49m\u001b[43m]\u001b[49m \u001b[38;5;241m=\u001b[39m \u001b[38;5;124m'\u001b[39m\u001b[38;5;124mx\u001b[39m\u001b[38;5;124m'\u001b[39m\n",
+      "\u001b[1;31mTypeError\u001b[0m: 'mappingproxy' object does not support item assignment"
+     ]
+    }
+   ],
+   "source": [
+    "d_proxy[2] = 'x'"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'B'"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "d[2] = 'B' \n",
+    "d_proxy[2]"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 3.8 集合论\n",
+    "\n",
+    "### 3.8.1 集合字面量\n",
+    "\n",
+    "空集必须要用`set()`来表示，因为`{}`表示的是空字典。当时1330还错过\n",
+    "\n",
+    "> Python特性\n",
+    "> 像{1, 2, 3} 这种字面量句法相比于构造方法（set([1, 2, 3])）要更快且更易读。后者的速度要慢一些，因为Python必须先从set这个名字来查询构造方法，然后新建一个列表，最后再把这个列表传入到构造方法里。但是如果是像{1, 2, 3}这样的字面量，Python会利用一个专门的叫作BUILD_SET的字节码来创建集合。\n",
+    "\n",
+    "`frozenset`没有字面量句法，只能通过构造方法来创建。\n",
+    "\n",
+    "### 3.8.2 集合推导\n",
+    "和列表推导式类似，只是用`{}`来代替`[]`。\n",
+    "\n",
+    "### 3.8.3 集合的操作\n",
+    "\n",
+    "有一些之前不太熟悉的就地修改操作：\n",
+    "- `s.update(t)` or `s |= t` union 就地修改\n",
+    "- `s.intersection_update(t)` or `s &= t` intersection 就地修改\n",
+    "- `s.difference_update(t)` or `s -= t` difference 就地修改\n",
+    "- `s.symmetric_difference_update(t)` or `s ^= t` symmetric difference 就地修改\n",
+    "\n",
+    "这里传入的参数可以是任何可迭代对象，包括集合，列表，生成器等(一个有趣的特性)\n",
+    "\n",
+    "返回值为bool的一些运算符：\n",
+    "- `s.isdisjoint(t)` 如果两个集合的交集为空，返回True\n",
+    "- `s.issubset(t)` 如果s中的每一个元素都在t中，返回True\n",
+    "- `s.issuperset(t)` 如果t中的每一个元素都在s中，返回True\n",
+    "\n",
+    "其他实用性方法：\n",
+    "- `s.add(e)` 添加元素\n",
+    "- `s.clear()` 清空集合\n",
+    "- `s.remove(e)` 删除元素，如果不存在会报错\n",
+    "- `s.discard(e)` 删除元素，如果不存在不会报错\n",
+    "- `s.copy()` 返回一个新的集合（浅拷贝）\n",
+    "- `s.pop()` 随机删除一个元素并返回\n",
+    "\n",
+    "## 3.9 dict和set的背后\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {