Merge pull request #104 from TabulateJarl8/main

Regex Presentation

regex/index.md

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+---
+marp: true
+theme: nord
+---
+
+# Regular Expressions
+
+Connor Sample - <https://tabulate.tech>
+
+---
+
+## <https://regex101.com>
+
+![Regex 101 documentation](regex101.png)
+
+---
+
+## What are regular expressions?
+
+- Sequences of characters that define a search pattern
+- Pattern matching and manipulation of text
+
+### Common use cases
+
+- Searching for specific patterns in log files
+- Parsing and extracting data from structured text
+- Validating input in scripts and programs
+- Utilies such as `grep`, `vim`, `sed`, and `awk` support regex
+
+---
+
+## Basic Syntax
+
+- **Literal characters:** `/hello/`
+- **Anchors:** Define positions within the text
+  - `/^start/`
+  - `/end$/`
+- **Or:** Combine two predicates together with the OR operator
+  - `/start|end/`
+
+---
+
+## Basic Syntax - Character classes
+
+- `/[a-z]/`
+- `/[A-Z0-9?]/`
+- `/[^A-Z]/`
+- The dot matches any character except line endings (`\n`, `\r`)
+  - `/c.t/`
+- Escape sequences can be used as shorthands
+  - `\s`
+  - `\d`
+  - `\t`
+
+---
+
+## Basic Syntax - Quantifiers
+
+- **Quantifiers:** Specify the number of occurrences
+  - `/[0-9]{3}/`
+  - `/[0-9]{3,5}/`
+  - `/[A-Za-z]*/`
+  - `/[A-Za-z]+/`
+  - `/[a-z]?/`
+
+---
+
+## Escaping special characters
+
+---
+
+### Examples
+
+1. **Finding patterns in files:**
+   - Use `grep` to search for specific strings or patterns
+   - `grep 'error' logfile.txt`
+   - `grep -E '([0-9]{1,3}\.){3}[0-9]{1,3}' access.log`
+
+2. **Replacing text in files:**
+   - Use `sed` or `awk` to perform find and replace operations
+   - `sed -i 's/\.html"/"/g' file.txt`
+
+3. **Validating input:**
+   - Ensure input adheres to specific formats or constraints
+   - `<input type="text" pattern="[A-Za-z]{3}"`
+
+---
+
+## Advanced Techniques
+
+- **Grouping and capturing:** Use parentheses to capture parts of a match
+  - **Text:** "Name: John, Age: 50"
+  - **Regex:** `Name: (\w+), Age: (\d+)`
+  - Non-capturing groups can be created as such: `(?:\w+)`
+- **Lookahead and lookbehind:** Specify conditions ahead or behind the match
+  - **Text:** "apple, banana, pear"
+  - **Regex:** `\w+(?=,)`
+  - **Text:** "apple - banana - pear"
+  - **Regex:** `(?<=-) \w+`
+
+---
+
+## Word Boundary Marker
+
+- `\b` to match the position between word characters and non word characters
+- Zero-width assertion
+- "this is test" vs "this is testing"
+
+---
+
+## More Advanced Techniques
+
+- **Backreferences:** Refer to captured groups
+  - **Text:** "Ray loves Python so so much"
+  - **Regex:** `(\b\w+\b) \1`
+
+- **Greedy vs lazy matching:** Control the greediness of quantifiers with `?`
+  - **Text:** `<div>Super</div> <p>Cool</p>`
+
+---
+
+### Example 1: Matching Digits
+
+**Text:** "I have 3 apples and 5 oranges."
+
+---
+
+### Example 1: Solution
+
+**Regex:** `\d+`
+
+---
+
+### Example 2: Matching Words with 3 characters
+
+`\b` can be used to match "word-boundaries", which is the space around word
+characters (`\w`).
+
+**Text:** "The quick brown fox jumps over the lazy dog."
+
+---
+
+### Example 2: Solution
+
+**Regex:** `\b\w{3}\b`
+
+---
+
+### Example 3: Matching Parts of a Date
+
+Use capture groups to extract `March`, `5`, and `2024`.
+**Text:** `March 5th, 2024`
+
+---
+
+### Example 3: Solution
+
+**Regex:** `([A-Za-z]+)\s+(\d{1,2})(?:[A-Za-z]*),\s+(\d{4})`
+
+---
+
+### Example 4: Matching Email Addresses
+
+**Text:** "Contact us at <[email protected]>."
+
+Simplified email specification:
+
+- Any uppercase or lowercase letters; numbers; the following symbols: `._%+-`
+
+Domain specification:
+
+- Any letter (case insensitive), numbers, or the hyphen.
+- Also support subdomains and TLDs of various lengths
+
+Use `\b` to ensure the email is standalone
+
+---
+
+### Example 4: Solution
+
+**Regex:** `\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}\b`
+
+---
+
+### Best practices
+
+- Don't create an overconvoluted and undocumented mess
+- Understand when you should and shouldn't use regex
+
+---
+
+[![h:700px](./old_email_regex.png)](https://pdw.ex-parrot.com/Mail-RFC822-Address.html)
+
+---
+
+```re
+(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:
+[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\
+[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)
++[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|
+[1-9]?[0-9]))\.){3}(?:(2(5[0-5]|[0-4][0-9])|1[0-9][0-9]|[1-9]?[0-9])|
+[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\
+[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])
+```
+
+---
+
+![h:700px](email_diagram.png)
+
+---
+
+```py
+import re
+
+pattern = re.compile(r"""
+\d+           # match one or more digits
+\.            # match the `.` character
+[A-Za-z]{5}   # match 5 letters of any case 
+""", re.X)
+
+pattern2 = re.compile(r"""
+(?x)  # verbose mode
+\d*   # match an optional digit
+""")
+```
+
+---
+
+## Q&A/Practice
+
+- Extract the three parts of a phone number with capturing groups
+- Parse dash-delimited dates (`2024-03-21`)
+- Write a regex to match URLs
+- Extract the parts of markdown links
+  - `[Display Text](https://tabulate.tech)`
+- Extract the arguments from a Python function signature:
+  - `def func(arg1, arg2):`