basic/36_regex.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Python 正则表达 RegEx"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 导入模块"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import re"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 简单 Python 匹配"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "False\n"
     ]
    }
   ],
   "source": [
    "# matching string\n",
    "pattern1 = \"cat\"\n",
    "pattern2 = \"bird\"\n",
    "string = \"dog runs to cat\"\n",
    "print(pattern1 in string)    \n",
    "print(pattern2 in string)    "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 用正则寻找配对"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(12, 15), match='cat'>\n",
      "None\n"
     ]
    }
   ],
   "source": [
    "# regular expression\n",
    "pattern1 = \"cat\"\n",
    "pattern2 = \"bird\"\n",
    "string = \"dog runs to cat\"\n",
    "print(re.search(pattern1, string))  \n",
    "print(re.search(pattern2, string)) "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 匹配多种可能 使用 []"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(4, 7), match='run'>\n"
     ]
    }
   ],
   "source": [
    "# multiple patterns (\"run\" or \"ran\")\n",
    "ptn = r\"r[au]n\"       \n",
    "print(re.search(ptn, \"dog runs to cat\"))    "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 匹配更多种可能"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "None\n",
      "<_sre.SRE_Match object; span=(4, 7), match='run'>\n",
      "<_sre.SRE_Match object; span=(4, 7), match='r2n'>\n",
      "<_sre.SRE_Match object; span=(4, 7), match='run'>\n"
     ]
    }
   ],
   "source": [
    "# continue\n",
    "print(re.search(r\"r[A-Z]n\", \"dog runs to cat\"))     \n",
    "print(re.search(r\"r[a-z]n\", \"dog runs to cat\"))     \n",
    "print(re.search(r\"r[0-9]n\", \"dog r2ns to cat\"))     \n",
    "print(re.search(r\"r[0-9a-z]n\", \"dog runs to cat\"))  "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 特殊种类匹配"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 数字"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(4, 7), match='r4n'>\n",
      "<_sre.SRE_Match object; span=(0, 3), match='run'>\n"
     ]
    }
   ],
   "source": [
    "# \\d : decimal digit\n",
    "print(re.search(r\"r\\dn\", \"run r4n\"))                \n",
    "# \\D : any non-decimal digit\n",
    "print(re.search(r\"r\\Dn\", \"run r4n\"))                \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 空白"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(0, 3), match='r\\nn'>\n",
      "<_sre.SRE_Match object; span=(4, 7), match='r4n'>\n"
     ]
    }
   ],
   "source": [
    "# \\s : any white space [\\t\\n\\r\\f\\v]\n",
    "print(re.search(r\"r\\sn\", \"r\\nn r4n\"))               \n",
    "# \\S : opposite to \\s, any non-white space\n",
    "print(re.search(r\"r\\Sn\", \"r\\nn r4n\"))               \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 所有字母数字和\"_\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(4, 7), match='r4n'>\n",
      "<_sre.SRE_Match object; span=(0, 3), match='r\\nn'>\n"
     ]
    }
   ],
   "source": [
    "# \\w : [a-zA-Z0-9_]\n",
    "print(re.search(r\"r\\wn\", \"r\\nn r4n\"))               \n",
    "# \\W : opposite to \\w\n",
    "print(re.search(r\"r\\Wn\", \"r\\nn r4n\"))               \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 空白字符"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(4, 8), match='runs'>\n",
      "<_sre.SRE_Match object; span=(5, 11), match=' runs '>\n"
     ]
    }
   ],
   "source": [
    "# \\b : empty string (only at the start or end of the word)\n",
    "print(re.search(r\"\\bruns\\b\", \"dog runs to cat\"))    \n",
    "# \\B : empty string (but not at the start or end of a word)\n",
    "print(re.search(r\"\\B runs \\B\", \"dog   runs  to cat\"))  \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 特殊字符 任意字符"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(0, 5), match='runs\\\\'>\n",
      "<_sre.SRE_Match object; span=(0, 3), match='r[n'>\n"
     ]
    }
   ],
   "source": [
    "# \\\\ : match \\\n",
    "print(re.search(r\"runs\\\\\", \"runs\\ to me\"))          \n",
    "# . : match anything (except \\n)\n",
    "print(re.search(r\"r.n\", \"r[ns to me\"))              \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 句尾句首"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(0, 3), match='dog'>\n",
      "<_sre.SRE_Match object; span=(12, 15), match='cat'>\n"
     ]
    }
   ],
   "source": [
    "# ^ : match line beginning\n",
    "print(re.search(r\"^dog\", \"dog runs to cat\"))        \n",
    "# $ : match line ending\n",
    "print(re.search(r\"cat$\", \"dog runs to cat\"))       \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 是否"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(0, 6), match='Monday'>\n",
      "<_sre.SRE_Match object; span=(0, 3), match='Mon'>\n"
     ]
    }
   ],
   "source": [
    "# ? : may or may not occur\n",
    "print(re.search(r\"Mon(day)?\", \"Monday\"))            \n",
    "print(re.search(r\"Mon(day)?\", \"Mon\"))               "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 多行匹配"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "None\n",
      "<_sre.SRE_Match object; span=(18, 19), match='I'>\n"
     ]
    }
   ],
   "source": [
    "# multi-line\n",
    "string = \"\"\"\n",
    "dog runs to cat.\n",
    "I run to dog.\n",
    "\"\"\"\n",
    "print(re.search(r\"^I\", string))                     \n",
    "print(re.search(r\"^I\", string, flags=re.M)) "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 0或多次"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(0, 1), match='a'>\n",
      "<_sre.SRE_Match object; span=(0, 6), match='abbbbb'>\n"
     ]
    }
   ],
   "source": [
    "# * : occur 0 or more times\n",
    "print(re.search(r\"ab*\", \"a\"))                       \n",
    "print(re.search(r\"ab*\", \"abbbbb\"))                  \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 1或多次"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "None\n",
      "<_sre.SRE_Match object; span=(0, 6), match='abbbbb'>\n"
     ]
    }
   ],
   "source": [
    "# + : occur 1 or more times\n",
    "print(re.search(r\"ab+\", \"a\"))                       \n",
    "print(re.search(r\"ab+\", \"abbbbb\"))                  \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 可选次数"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "None\n",
      "<_sre.SRE_Match object; span=(0, 6), match='abbbbb'>\n"
     ]
    }
   ],
   "source": [
    "# {n, m} : occur n to m times\n",
    "print(re.search(r\"ab{2,10}\", \"a\"))                  \n",
    "print(re.search(r\"ab{2,10}\", \"abbbbb\"))             \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## group 组"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "021523, Date: Feb/12/2017\n",
      "021523\n",
      "Feb/12/2017\n"
     ]
    }
   ],
   "source": [
    "# group\n",
    "match = re.search(r\"(\\d+), Date: (.+)\", \"ID: 021523, Date: Feb/12/2017\")\n",
    "print(match.group())                                \n",
    "print(match.group(1))                               \n",
    "print(match.group(2))                               "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "021523\n",
      "Feb/12/2017\n"
     ]
    }
   ],
   "source": [
    "match = re.search(r\"(?P<id>\\d+), Date: (?P<date>.+)\", \"ID: 021523, Date: Feb/12/2017\")\n",
    "print(match.group('id'))                            \n",
    "print(match.group('date'))                          "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 寻找所有匹配 "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['run', 'ran']\n"
     ]
    }
   ],
   "source": [
    "# findall\n",
    "print(re.findall(r\"r[ua]n\", \"run ran ren\"))         "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['run', 'ran']\n"
     ]
    }
   ],
   "source": [
    "# | : or\n",
    "print(re.findall(r\"(run|ran)\", \"run ran ren\"))      "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 替换"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "dog catches to cat\n"
     ]
    }
   ],
   "source": [
    "# re.sub() replace\n",
    "print(re.sub(r\"r[au]ns\", \"catches\", \"dog runs to cat\"))     "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 分裂"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['a', 'b', 'c', 'd', 'e']\n"
     ]
    }
   ],
   "source": [
    "# re.split()\n",
    "print(re.split(r\"[,;\\.]\", \"a;b,c.d;e\"))             \n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## compile"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<_sre.SRE_Match object; span=(4, 7), match='ran'>\n"
     ]
    }
   ],
   "source": [
    "# compile\n",
    "compiled_re = re.compile(r\"r[ua]n\")\n",
    "print(compiled_re.search(\"dog ran to cat\"))     "
   ]
  }
 ],
 "metadata": {
  "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",
   "version": "3.5.1"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 1
}