{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 日志视图\n",
    "\n",
    "创建一个日志视图，允许添加新行而无需将整个历史记录重新发送给客户端。\n",
    "\n",
    "`max_lines`: 在丢弃最旧的行之前的最大行数（默认：`None`）"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<nicegui.elements.button.Button at 0x2c61e05b290>"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "from datetime import datetime\n",
    "from nicegui import ui\n",
    "\n",
    "log = ui.log(max_lines=10).classes('w-full h-20')\n",
    "ui.button('Log time', on_click=lambda: log.push(datetime.now().strftime('%X.%f')[:-5]))\n",
    "\n",
    "# ui.run()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 附加日志\n",
    "\n",
    "你可以将一个`ui.log`元素附加到一个Python日志记录器对象上，这样日志消息就会被推送到日志元素中。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<nicegui.elements.button.Button at 0x2c61d089910>"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "import logging\n",
    "from datetime import datetime\n",
    "from nicegui import ui\n",
    "\n",
    "logger = logging.getLogger()\n",
    "\n",
    "class LogElementHandler(logging.Handler):\n",
    "    \"\"\"A logging handler that emits messages to a log element.\"\"\"\n",
    "\n",
    "    def __init__(self, element: ui.log, level: int = logging.NOTSET) -> None:\n",
    "        self.element = element\n",
    "        super().__init__(level)\n",
    "\n",
    "    def emit(self, record: logging.LogRecord) -> None:\n",
    "        try:\n",
    "            msg = self.format(record)\n",
    "            self.element.push(msg)\n",
    "        except Exception:\n",
    "            self.handleError(record)\n",
    "\n",
    "log = ui.log(max_lines=10).classes('w-full')\n",
    "logger.addHandler(LogElementHandler(log))\n",
    "ui.button('Log time', on_click=lambda: logger.warning(datetime.now().strftime('%X.%f')[:-5]))\n",
    "\n",
    "# ui.run()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
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