14. Pandas实现数据的合并concat.ipynb

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   "source": [
    "## Pandas实现数据的合并concat"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### 使用场景：\n",
    "批量合并相同格式的Excel、给DataFrame添加行、给DataFrame添加列\n",
    "\n",
    "#### 一句话说明concat语法：  \n",
    "* 使用某种合并方式(inner/outer)\n",
    "* 沿着某个轴向(axis=0/1)\n",
    "* 把多个Pandas对象(DataFrame/Series)合并成一个。\n",
    "\n",
    "#### concat语法：pandas.concat(objs, axis=0, join='outer', ignore_index=False)\n",
    "* objs：一个列表，内容可以是DataFrame或者Series，可以混合\n",
    "* axis：默认是0代表按行合并，如果等于1代表按列合并\n",
    "* join：合并的时候索引的对齐方式，默认是outer join，也可以是inner join\n",
    "* ignore_index：是否忽略掉原来的数据索引\n",
    "\n",
    "#### append语法：DataFrame.append(other, ignore_index=False)\n",
    "append只有按行合并，没有按列合并，相当于concat按行的简写形式  \n",
    "* other：单个dataframe、series、dict，或者列表\n",
    "* ignore_index：是否忽略掉原来的数据索引\n",
    "\n",
    "#### 参考文档：\n",
    "* pandas.concat的api文档：https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.concat.html\n",
    "* pandas.concat的教程：https://pandas.pydata.org/pandas-docs/stable/user_guide/merging.html\n",
    "* pandas.append的api文档：https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.append.html"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import pandas as pd\n",
    "\n",
    "import warnings\n",
    "warnings.filterwarnings('ignore')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 一、使用pandas.concat合并数据"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
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   "outputs": [
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       "    A   B   C   D   E\n",
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       "2  A2  B2  C2  D2  E2\n",
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    "df1 = pd.DataFrame({'A': ['A0', 'A1', 'A2', 'A3'],\n",
    "                    'B': ['B0', 'B1', 'B2', 'B3'],\n",
    "                    'C': ['C0', 'C1', 'C2', 'C3'],\n",
    "                    'D': ['D0', 'D1', 'D2', 'D3'],\n",
    "                    'E': ['E0', 'E1', 'E2', 'E3']\n",
    "                   })\n",
    "df1"
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       "    A   B   C   D   F\n",
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    "df2 = pd.DataFrame({ 'A': ['A4', 'A5', 'A6', 'A7'],\n",
    "                     'B': ['B4', 'B5', 'B6', 'B7'],\n",
    "                     'C': ['C4', 'C5', 'C6', 'C7'],\n",
    "                     'D': ['D4', 'D5', 'D6', 'D7'],\n",
    "                     'F': ['F4', 'F5', 'F6', 'F7']\n",
    "                   })\n",
    "df2"
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***1、默认的concat，参数为axis=0、join=outer、ignore_index=False***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
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       "    A   B   C   D    E    F\n",
       "0  A0  B0  C0  D0   E0  NaN\n",
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       "2  A2  B2  C2  D2   E2  NaN\n",
       "3  A3  B3  C3  D3   E3  NaN\n",
       "0  A4  B4  C4  D4  NaN   F4\n",
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     "execution_count": 4,
     "metadata": {},
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   "source": [
    "pd.concat([df1,df2])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***2、使用ignore_index=True可以忽略原来的索引***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
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       "    A   B   C   D    E    F\n",
       "0  A0  B0  C0  D0   E0  NaN\n",
       "1  A1  B1  C1  D1   E1  NaN\n",
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       "6  A6  B6  C6  D6  NaN   F6\n",
       "7  A7  B7  C7  D7  NaN   F7"
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     "execution_count": 5,
     "metadata": {},
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   "source": [
    "pd.concat([df1,df2], ignore_index=True)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***3、使用join=inner过滤掉不匹配的列***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
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       "    A   B   C   D\n",
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   ],
   "source": [
    "pd.concat([df1,df2], ignore_index=True, join=\"inner\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***4、使用axis=1相当于添加新列***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
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       "\n",
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       "      <td>1</td>\n",
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       "      <td>C1</td>\n",
       "      <td>D1</td>\n",
       "      <td>E1</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>2</td>\n",
       "      <td>A2</td>\n",
       "      <td>B2</td>\n",
       "      <td>C2</td>\n",
       "      <td>D2</td>\n",
       "      <td>E2</td>\n",
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       "    <tr>\n",
       "      <td>3</td>\n",
       "      <td>A3</td>\n",
       "      <td>B3</td>\n",
       "      <td>C3</td>\n",
       "      <td>D3</td>\n",
       "      <td>E3</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "    A   B   C   D   E\n",
       "0  A0  B0  C0  D0  E0\n",
       "1  A1  B1  C1  D1  E1\n",
       "2  A2  B2  C2  D2  E2\n",
       "3  A3  B3  C3  D3  E3"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "df1"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***A：添加一列Series***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
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       "\n",
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       "      <td>E0</td>\n",
       "      <td>0</td>\n",
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       "    <tr>\n",
       "      <td>1</td>\n",
       "      <td>A1</td>\n",
       "      <td>B1</td>\n",
       "      <td>C1</td>\n",
       "      <td>D1</td>\n",
       "      <td>E1</td>\n",
       "      <td>1</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>2</td>\n",
       "      <td>A2</td>\n",
       "      <td>B2</td>\n",
       "      <td>C2</td>\n",
       "      <td>D2</td>\n",
       "      <td>E2</td>\n",
       "      <td>2</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>3</td>\n",
       "      <td>A3</td>\n",
       "      <td>B3</td>\n",
       "      <td>C3</td>\n",
       "      <td>D3</td>\n",
       "      <td>E3</td>\n",
       "      <td>3</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "    A   B   C   D   E  F\n",
       "0  A0  B0  C0  D0  E0  0\n",
       "1  A1  B1  C1  D1  E1  1\n",
       "2  A2  B2  C2  D2  E2  2\n",
       "3  A3  B3  C3  D3  E3  3"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "s1 = pd.Series(list(range(4)), name=\"F\")\n",
    "pd.concat([df1,s1], axis=1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***B：添加多列Series***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [],
   "source": [
    "s2 = df1.apply(lambda x:x[\"A\"]+\"_GG\", axis=1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0    A0_GG\n",
       "1    A1_GG\n",
       "2    A2_GG\n",
       "3    A3_GG\n",
       "dtype: object"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "s2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [],
   "source": [
    "s2.name=\"G\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
       "        vertical-align: middle;\n",
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       "\n",
       "    .dataframe tbody tr th {\n",
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       "\n",
       "    .dataframe thead th {\n",
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       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
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       "      <td>A0_GG</td>\n",
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       "      <td>1</td>\n",
       "      <td>A1_GG</td>\n",
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       "    <tr>\n",
       "      <td>2</td>\n",
       "      <td>A2</td>\n",
       "      <td>B2</td>\n",
       "      <td>C2</td>\n",
       "      <td>D2</td>\n",
       "      <td>E2</td>\n",
       "      <td>2</td>\n",
       "      <td>A2_GG</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>3</td>\n",
       "      <td>A3</td>\n",
       "      <td>B3</td>\n",
       "      <td>C3</td>\n",
       "      <td>D3</td>\n",
       "      <td>E3</td>\n",
       "      <td>3</td>\n",
       "      <td>A3_GG</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "    A   B   C   D   E  F      G\n",
       "0  A0  B0  C0  D0  E0  0  A0_GG\n",
       "1  A1  B1  C1  D1  E1  1  A1_GG\n",
       "2  A2  B2  C2  D2  E2  2  A2_GG\n",
       "3  A3  B3  C3  D3  E3  3  A3_GG"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "pd.concat([df1,s1,s2], axis=1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
       "        vertical-align: middle;\n",
       "    }\n",
       "\n",
       "    .dataframe tbody tr th {\n",
       "        vertical-align: top;\n",
       "    }\n",
       "\n",
       "    .dataframe thead th {\n",
       "        text-align: right;\n",
       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
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       "    <tr style=\"text-align: right;\">\n",
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       "      <td>0</td>\n",
       "      <td>A0_GG</td>\n",
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       "    <tr>\n",
       "      <td>1</td>\n",
       "      <td>1</td>\n",
       "      <td>A1_GG</td>\n",
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       "    <tr>\n",
       "      <td>2</td>\n",
       "      <td>2</td>\n",
       "      <td>A2_GG</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>3</td>\n",
       "      <td>3</td>\n",
       "      <td>A3_GG</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "   F      G\n",
       "0  0  A0_GG\n",
       "1  1  A1_GG\n",
       "2  2  A2_GG\n",
       "3  3  A3_GG"
      ]
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     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# 列表可以只有Series\n",
    "pd.concat([s1,s2], axis=1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
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       "\n",
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       "        vertical-align: top;\n",
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       "\n",
       "    .dataframe thead th {\n",
       "        text-align: right;\n",
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       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
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       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>F</th>\n",
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       "      <th>C</th>\n",
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       "      <th>G</th>\n",
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       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <td>0</td>\n",
       "      <td>0</td>\n",
       "      <td>A0</td>\n",
       "      <td>B0</td>\n",
       "      <td>C0</td>\n",
       "      <td>D0</td>\n",
       "      <td>E0</td>\n",
       "      <td>A0_GG</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>1</td>\n",
       "      <td>1</td>\n",
       "      <td>A1</td>\n",
       "      <td>B1</td>\n",
       "      <td>C1</td>\n",
       "      <td>D1</td>\n",
       "      <td>E1</td>\n",
       "      <td>A1_GG</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>2</td>\n",
       "      <td>2</td>\n",
       "      <td>A2</td>\n",
       "      <td>B2</td>\n",
       "      <td>C2</td>\n",
       "      <td>D2</td>\n",
       "      <td>E2</td>\n",
       "      <td>A2_GG</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>3</td>\n",
       "      <td>3</td>\n",
       "      <td>A3</td>\n",
       "      <td>B3</td>\n",
       "      <td>C3</td>\n",
       "      <td>D3</td>\n",
       "      <td>E3</td>\n",
       "      <td>A3_GG</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "   F   A   B   C   D   E      G\n",
       "0  0  A0  B0  C0  D0  E0  A0_GG\n",
       "1  1  A1  B1  C1  D1  E1  A1_GG\n",
       "2  2  A2  B2  C2  D2  E2  A2_GG\n",
       "3  3  A3  B3  C3  D3  E3  A3_GG"
      ]
     },
     "execution_count": 14,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# 列表是可以混合顺序的\n",
    "pd.concat([s1,df1,s2], axis=1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 二、使用DataFrame.append按行合并数据"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
       "        vertical-align: middle;\n",
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       "\n",
       "    .dataframe tbody tr th {\n",
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       "\n",
       "    .dataframe thead th {\n",
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       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>A</th>\n",
       "      <th>B</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <td>0</td>\n",
       "      <td>1</td>\n",
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       "    </tr>\n",
       "    <tr>\n",
       "      <td>1</td>\n",
       "      <td>3</td>\n",
       "      <td>4</td>\n",
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       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "   A  B\n",
       "0  1  2\n",
       "1  3  4"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "df1 = pd.DataFrame([[1, 2], [3, 4]], columns=list('AB'))\n",
    "df1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
       "        vertical-align: middle;\n",
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       "\n",
       "    .dataframe tbody tr th {\n",
       "        vertical-align: top;\n",
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       "\n",
       "    .dataframe thead th {\n",
       "        text-align: right;\n",
       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>A</th>\n",
       "      <th>B</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
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       "      <td>6</td>\n",
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       "    <tr>\n",
       "      <td>1</td>\n",
       "      <td>7</td>\n",
       "      <td>8</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "   A  B\n",
       "0  5  6\n",
       "1  7  8"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "df2 = pd.DataFrame([[5, 6], [7, 8]], columns=list('AB'))\n",
    "df2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***1、给1个dataframe添加另一个dataframe***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
       "        vertical-align: middle;\n",
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       "\n",
       "    .dataframe tbody tr th {\n",
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       "\n",
       "    .dataframe thead th {\n",
       "        text-align: right;\n",
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       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>A</th>\n",
       "      <th>B</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <td>0</td>\n",
       "      <td>1</td>\n",
       "      <td>2</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>1</td>\n",
       "      <td>3</td>\n",
       "      <td>4</td>\n",
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       "    <tr>\n",
       "      <td>0</td>\n",
       "      <td>5</td>\n",
       "      <td>6</td>\n",
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       "    <tr>\n",
       "      <td>1</td>\n",
       "      <td>7</td>\n",
       "      <td>8</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "   A  B\n",
       "0  1  2\n",
       "1  3  4\n",
       "0  5  6\n",
       "1  7  8"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "df1.append(df2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***2、忽略原来的索引ignore_index=True***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
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       "    <tr style=\"text-align: right;\">\n",
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       "   A  B\n",
       "0  1  2\n",
       "1  3  4\n",
       "2  5  6\n",
       "3  7  8"
      ]
     },
     "execution_count": 18,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "df1.append(df2, ignore_index=True)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***3、可以一行一行的给DataFrame添加数据***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
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       "\n",
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      "text/plain": [
       "Empty DataFrame\n",
       "Columns: [A]\n",
       "Index: []"
      ]
     },
     "execution_count": 19,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# 一个空的df\n",
    "df = pd.DataFrame(columns=['A'])\n",
    "df"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***A：低性能版本***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
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       "    .dataframe tbody tr th:only-of-type {\n",
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       "      <td>3</td>\n",
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      "text/plain": [
       "   A\n",
       "0  0\n",
       "1  1\n",
       "2  2\n",
       "3  3\n",
       "4  4"
      ]
     },
     "execution_count": 20,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "for i in range(5):\n",
    "    # 注意这里每次都在复制\n",
    "    df = df.append({'A': i}, ignore_index=True)\n",
    "df"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "***B：性能好的版本***"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style scoped>\n",
       "    .dataframe tbody tr th:only-of-type {\n",
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       "\n",
       "    .dataframe tbody tr th {\n",
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       "      <td>1</td>\n",
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       "    <tr>\n",
       "      <td>2</td>\n",
       "      <td>2</td>\n",
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       "    <tr>\n",
       "      <td>3</td>\n",
       "      <td>3</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <td>4</td>\n",
       "      <td>4</td>\n",
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      "text/plain": [
       "   A\n",
       "0  0\n",
       "1  1\n",
       "2  2\n",
       "3  3\n",
       "4  4"
      ]
     },
     "execution_count": 21,
     "metadata": {},
     "output_type": "execute_result"
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   ],
   "source": [
    "# 第一个入参是一个列表，避免了多次复制\n",
    "pd.concat(\n",
    "    [pd.DataFrame([i], columns=['A']) for i in range(5)],\n",
    "    ignore_index=True\n",
    ")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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