From 57a7bbdad165cb823be05fd30fda2297b6c3bf24 Mon Sep 17 00:00:00 2001
From: p46318075 <2872608952@qq.com>
Date: Mon, 2 Dec 2024 12:06:39 +0800
Subject: [PATCH] ADD file via upload

---
 3 变量作用域.ipynb | 208 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 208 insertions(+)
 create mode 100644 3 变量作用域.ipynb

diff --git a/3 变量作用域.ipynb b/3 变量作用域.ipynb
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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 变量的作用域\n",
+    "\n",
+    "变量的作用域（scope）决定了变量可以被访问和使用的代码区域。\n",
+    "\n",
+    "在Python中，变量的作用域主要有以下几种类型：\n",
+    " - 局部作用域 (Local Scope):函数内部定义的变量, 仅在函数内部可见可用。\n",
+    " - 嵌套作用域 (Enclosing Scope):在嵌套函数中，外部函数的变量对内部函数可见。\n",
+    " - 全局作用域 (Global Scope): 在所有函数外部定义的变量，可以在整个程序中被访问。\n",
+    " - 内置作用域 (Built-in Scope): 包含Python内置函数、变量和异常等。最外层作用域。   "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### 局部变量和全局变量\n",
+    " - 赋值运算默认创建局部变量"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 24,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "10\n",
+      "10\n"
+     ]
+    }
+   ],
+   "source": [
+    "x = 10  # 全局变量\n",
+    "\n",
+    "def ff():\n",
+    "    y = 5  # 赋值运算默认创建局部变量\n",
+    "    print(x)  # 可以访问全局变量 x\n",
+    "\n",
+    "ff()  # 调用函数，输出10\n",
+    "print(x)  # 输出全局变量x的值，仍然是10\n",
+    "# print(y)  # 出错，y 在 ff 内部定义，是局部变量，在函数外部无法访问"
+   ]
+  },
+  {
+   "cell_type": "raw",
+   "metadata": {},
+   "source": [
+    "''' 特别注意：下面代码发生错误。\n",
+    "因为执行到 x = x + 2 ，首先将 x 登记为局部变量，\n",
+    "接着计算右边的x + 2时，x还未被定义，所以会报错。\n",
+    "'''\n",
+    "x  = 10\n",
+    "\n",
+    "def ff():    \n",
+    "   x = x + 2   #  x += 2 等价\n",
+    "    \n",
+    "ff()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### 函数嵌套\n",
+    "\n",
+    "Python 变量访问优先级规则(LEGB)，这也是变量的遮蔽顺序：Local（局部作用域） -> Enclosing（嵌套作用域） -> Global（全局作用域） -> Built-in（内置作用域）\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 25,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "2\n",
+      "5\n",
+      "10\n"
+     ]
+    }
+   ],
+   "source": [
+    "x = 10  # 全局变量\n",
+    "\n",
+    "def outer():\n",
+    "    x = 5  # outer函数的局部变量\n",
+    "\n",
+    "    def inner():\n",
+    "        x = 2  # inner函数的局部变量\n",
+    "        print(x)  # 输出局部变量x的值\n",
+    "\n",
+    "    inner()  # 输出2\n",
+    "    print(x)  # 输出outer函数的局部变量x的值，即 5\n",
+    "\n",
+    "outer()  # 调用outer函数\n",
+    "print(x)  # 输出全局变量x的值，即10"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### 如果打算给非局部变量赋值，需要特别申明"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "###  global 关键字功能\n",
+    "\n",
+    "想在函数内部修改全局变量，使用global关键字。"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "5\n"
+     ]
+    }
+   ],
+   "source": [
+    "x = 10  # 全局变量\n",
+    "\n",
+    "def func():\n",
+    "    global x  # 声明使用全局变量 x\n",
+    "    x = 5    # 修改全局变量 x 的值\n",
+    "\n",
+    "func()  # 调用函数，修改全局变量x的值\n",
+    "print(x)  # 输出全局变量x的新值，现在是 5"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### nonlocal 关键字功能\n",
+    "\n",
+    "函数嵌套时，如果想修改外层函数的局部变量，需要使用nonlocal关键字。"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "10\n"
+     ]
+    }
+   ],
+   "source": [
+    "def outer():\n",
+    "    x = 5  # outer函数的局部变量\n",
+    "\n",
+    "    def inner():\n",
+    "        nonlocal x  # 声明x是outer函数的局部变量，而不是全局变量\n",
+    "        x = 10     # 修改outer函数的局部变量x的值\n",
+    "\n",
+    "    inner()  # 调用inner函数\n",
+    "    print(x)  # 输出修改后的x值，即10\n",
+    "\n",
+    "outer()  # 调用outer函数"
+   ]
+  }
+ ],
+ "metadata": {
+  "hide_input": false,
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
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+ "nbformat": 4,
+ "nbformat_minor": 4
+}