Update python高级知识.ipynb

Author: aopstudio

面试相关/python高级知识.ipynb

@@ -308,12 +308,103 @@
     "c.greeting()"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 变量范围"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Python寻找变量的过程：本地范围->模块范围->Built-in范围"
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [],
-   "source": []
+   "source": [
+    "count = 10\n",
+    "def greeting(flag):\n",
+    "    if flag:\n",
+    "        count = 20\n",
+    "    print(count)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "20\n"
+     ]
+    }
+   ],
+   "source": [
+    "greeting(True)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "UnboundLocalError",
+     "evalue": "local variable 'count' referenced before assignment",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mUnboundLocalError\u001b[0m                         Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn [4], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mgreeting\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;28;43;01mFalse\u001b[39;49;00m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn [2], line 5\u001b[0m, in \u001b[0;36mgreeting\u001b[0;34m(flag)\u001b[0m\n\u001b[1;32m      3\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m flag:\n\u001b[1;32m      4\u001b[0m     count \u001b[38;5;241m=\u001b[39m \u001b[38;5;241m20\u001b[39m\n\u001b[0;32m----> 5\u001b[0m \u001b[38;5;28mprint\u001b[39m(\u001b[43mcount\u001b[49m)\n",
+      "\u001b[0;31mUnboundLocalError\u001b[0m: local variable 'count' referenced before assignment"
+     ]
+    }
+   ],
+   "source": [
+    "greeting(False) # 会报错，因为在编译时python会创建本地范围的count定义，而运行时却发现没有值"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "函数内global定义的变量可以修改外部的变量值"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "20\n",
+      "20\n"
+     ]
+    }
+   ],
+   "source": [
+    "count = 10\n",
+    "def greeting(flag):\n",
+    "    global count\n",
+    "    if flag:\n",
+    "        count = 20\n",
+    "    print(count)\n",
+    "greeting(True)\n",
+    "print(count)"
+   ]
   }
  ],
  "metadata": {
@@ -332,7 +423,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.1"
+   "version": "3.9.6"
   }
  },
  "nbformat": 4,