{ "cells": [ { "cell_type": "markdown", "id": "e1c7e284", "metadata": {}, "source": [ "# Advanced Topics" ] }, { "cell_type": "code", "execution_count": null, "id": "abaf523a", "metadata": {}, "outputs": [], "source": [ "import sys\n", "from pathlib import Path\n", "\n", "# Find project root by looking for _config.yml\n", "current = Path.cwd()\n", "for parent in [current, *current.parents]:\n", " if (parent / '_config.yml').exists():\n", " project_root = parent\n", " break\n", "else:\n", " project_root = Path.cwd().parent.parent\n", "\n", "# Add project root to path\n", "sys.path.insert(0, str(project_root))\n", "\n", "# Import shared teaching helpers and cell magics\n", "from shared import thinkpython, diagram, jupyturtle, structshape\n", "from shared.download import download\n" ] }, { "cell_type": "code", "execution_count": null, "id": "f9f93d6b", "metadata": {}, "outputs": [], "source": [ "import re\n" ] }, { "cell_type": "markdown", "id": "2ee22e3c", "metadata": {}, "source": [ "## Flags\n", "\n", "Flags change matching behavior:\n", "\n", "| Flag | Shorthand | Meaning |\n", "|---|---|---|\n", "| `re.IGNORECASE` | `re.I` | Case-insensitive matching |\n", "| `re.MULTILINE` | `re.M` | `^`/`$` match line start/end |\n", "| `re.DOTALL` | `re.S` | `.` matches newline too |\n", "| `re.VERBOSE` | `re.X` | Allow comments/whitespace in pattern |" ] }, { "cell_type": "code", "execution_count": 65, "id": "4d3245a1", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['Hello', 'HELLO', 'hello']\n", "['
\\nsome content\\n
']\n", "['hello@example.com', 'support@test.org']\n" ] } ], "source": [ "# IGNORECASE\n", "print(re.findall(r\"hello\", \"Hello HELLO hello\", re.I)) # ['Hello', 'HELLO', 'hello']\n", "\n", "# DOTALL — dot matches newline\n", "text = \"
\\nsome content\\n
\"\n", "print(re.findall(r\"
.*
\", text, re.DOTALL)) # matches across lines\n", "\n", "# VERBOSE — write readable patterns with comments\n", "email_pattern = re.compile(r\"\"\"\n", " [\\w.+-]+ # username\n", " @ # at sign\n", " [\\w-]+ # domain name\n", " \\. # dot\n", " [\\w.]+ # TLD\n", "\"\"\", re.VERBOSE)\n", "\n", "print(email_pattern.findall(\"Contact us at hello@example.com or support@test.org\"))" ] }, { "cell_type": "code", "execution_count": null, "id": "f7afa4c2", "metadata": { "tags": [ "thebe-interactive" ] }, "outputs": [], "source": [ "### EXERCISE: Regex Flags\n", "# Difficulty: Basic\n", "import re\n", "log = \"\"\"INFO: Server started\n", "error: disk full\n", "WARNING: low memory\n", "ERROR: connection lost\"\"\"\n", "# 1. Use re.findall() with re.IGNORECASE | re.MULTILINE to\n", "# extract every line that begins with 'error'\n", "# 2. Print the list of matches\n", "### Your code starts here:\n", "\n", "\n", "\n", "### Your code ends here." ] }, { "cell_type": "code", "execution_count": null, "id": "15265b18", "metadata": { "tags": [ "hide-input" ] }, "outputs": [], "source": [ "# Solution\n", "import re\n", "log = \"\"\"INFO: Server started\n", "error: disk full\n", "WARNING: low memory\n", "ERROR: connection lost\"\"\"\n", "results = re.findall(r'^error.*$', log, flags=re.IGNORECASE | re.MULTILINE)\n", "print(results)" ] }, { "cell_type": "markdown", "id": "e898c620", "metadata": {}, "source": [ "## Compiled Patterns\n", "Use `re.compile()` when reusing the same pattern multiple times — more efficient and cleaner." ] }, { "cell_type": "code", "execution_count": 66, "id": "1c2b8f29", "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Found: ['123-456-7890'] in 'Call me at 123-456-7890'\n", "Found: ['987.654.3210'] in 'My number is 987.654.3210'\n", "Found: ['555-123-4567', '800-999-0000'] in 'Reach us at 555-123-4567 or 800-999-0000'\n" ] } ], "source": [ "# Compile once, use many times\n", "phone_pattern = re.compile(r\"\\b\\d{3}[-.]\\d{3}[-.]\\d{4}\\b\")\n", "\n", "texts = [\n", " \"Call me at 123-456-7890\",\n", " \"My number is 987.654.3210\",\n", " \"No phone here\",\n", " \"Reach us at 555-123-4567 or 800-999-0000\"\n", "]\n", "\n", "for t in texts:\n", " matches = phone_pattern.findall(t)\n", " if matches:\n", " print(f\"Found: {matches} in '{t}'\")" ] }, { "cell_type": "code", "execution_count": null, "id": "2c84d8f4", "metadata": { "tags": [ "thebe-interactive" ] }, "outputs": [], "source": [ "### EXERCISE: Compiled Patterns\n", "# Difficulty: Basic\n", "import re\n", "emails = ['alice@example.com', 'not-an-email', 'bob@company.org', 'charlie_at_test.net']\n", "# 1. Compile a regex pattern that matches a simple email address\n", "# 2. Print each email with True or False using the compiled pattern\n", "### Your code starts here:\n", "\n", "\n", "\n", "### Your code ends here." ] }, { "cell_type": "code", "execution_count": null, "id": "d023474f", "metadata": { "tags": [ "hide-input" ] }, "outputs": [], "source": [ "# Solution\n", "import re\n", "emails = ['alice@example.com', 'not-an-email', 'bob@company.org', 'charlie_at_test.net']\n", "email_re = re.compile(r'[\\w.+-]+@[\\w-]+\\.[\\w.]+')\n", "for e in emails:\n", " print(e, bool(email_re.fullmatch(e)))" ] }, { "cell_type": "markdown", "id": "f90ad03b", "metadata": {}, "source": [ "## Lookahead & Lookbehind\n", "\n", "Match a pattern only if it is (or isn't) preceded/followed by another pattern — without including that other pattern in the match.\n", "\n", "| Syntax | Type | Meaning |\n", "|---|---|---|\n", "| `(?=...)` | Positive lookahead | Followed by |\n", "| `(?!...)` | Negative lookahead | NOT followed by |\n", "| `(?<=...)` | Positive lookbehind | Preceded by |\n", "| `(?