Regex Cheatsheet 101: Your Ticket to Regex Mastery

Regex Cheatsheet 101

Are you tired of trying to make sense of regex? Don't worry, you're not alone! Regex is like a secret language that only a select few seem to understand.

We've got you covered with our Regex Cheatsheet 101!

NOTE: This blog is visually unappealing due to the formatting of dev so I am also linking my blog where it looks better.

Anchors

• ^: Start of string or line. Think of it as a hat for your text. It marks the beginning of a line.
• \A: Start of string. A fancier hat that marks the beginning of a string.
• $: End of string or line. The opposite of ^, it marks the end of a line.
• \Z: End of string. The fancier cousin of $ that marks the end of a string.
• \b: Word boundary. It's like a little force field around a word that tells you where it begins and ends.
• \B: Not word boundary. The opposite of \b.
• \<: Start of word. Similar to ^ and \A, but specifically for words.
• \>: End of word. The opposite of \<.

Character Classes

• \c: Control character. A character that controls your text. Watch out, it's in charge!
• \s: Whitespace. Spaces, tabs, and other invisible characters that make your text look nice and neat.
• \S: Not whitespace. Anything that's not a space, tab, or other invisible character.
• \d: Digit. The numbers 0-9.
• \D: Not digit. Anything that's not a number.
• \w: Word. Letters, numbers, and underscores.
• \W: Not word. Anything that's not a letter, number, or underscore.
• \x: Hexadecimal digit. A fancy name for numbers and letters (A-F, a-f) that are used in hex code.
• \O: Octal digit. Numbers in base 8. Fun fact: octopuses are also good with digits!

Quantifiers

• *: 0 or more. Like a buffet that you can go back to as many times as you want.
• +: 1 or more. Like a VIP lounge that only lets in the cool kids who have something to offer.
• ?: 0 or 1 (optional). Like a checkbox that you can check or leave empty.
• {3}: Exactly 3. The perfect number of times to do something.
• {3,}: 3 or more. Like a marathon that never seems to end.
• {2,5}: 2, 3, 4 or 5. Like a multiple-choice question with several correct answers.

Special Characters

• \n: New line. The line break that you use when you want to start a new paragraph.
• \r: Carriage return. A fancy name for the Enter key.
• \t: Tab. The button that you press when you want to indent your text.
• \v: Vertical tab. A rarely used character that you probably won't need to worry about.
• \f: Form feed. A character that's mostly used in old printers. Don't worry about it.

Assertions

• ?=: Lookahead assertion. Like a crystal ball that tells you what's coming up next in your text.
• ?!: Negative lookahead. The opposite of ?=. It tells you what's not coming up next in your text.
• ?<=: Lookbehind assertion. Like a time machine that takes you back to the beginning of a word or phrase.
• ?<!: Negative lookbehind. The opposite of ?<=. It tells you what's not behind you in your text.

Groups and Capture

• (): Group. A way to group parts of your regex together.
• (?:): Non-capturing group. Like a regular group, but it doesn't create a capture group.
• \n: Backreference. A way to reference a previous capture group.
• (?P<name>): Named capture group. A way to give a capture group a name.

Alternation

• |: Alternation. A way to match one thing or another. It's like a fork in the road.
• []: Character set. A way to match one character out of a set of characters.
• [^]: Negated character set. The opposite of []. Matches anything not in the set.

Flags

• i: Case-insensitive. Matches both upper and lowercase letters.
• m: Multiline. Allows ^ and $ to match the beginning and end of lines.
• s: Dot-all. Allows . to match newline characters.
• x: Verbose. Allows you to write your regex in multiple lines and add comments.

Family Friendly Examples

• Match the first word of a sentence:

^\w+

• Match the whole text except for the last line:

^.*\n.*\n.*$

• Find all the words that contain the letter "z":

\b\w*z\w*\b

• Find all the words that do not contain the letter "e":

\b[^e\s]+\b

• Match any line that starts with a digit:

^\d.*$

• Match any line that ends with a punctuation mark:

^.*\p{P}$

• Find all the phone numbers in a text:

(\d{3})-(\d{3})-(\d{4})

• Find all the email addresses in a text:

\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b

• Match any line that starts with the word "Lorem":

^\bLorem\b.*$

• Match any line that ends with a three-digit number:

^.*\b\d{3}$

• Match any line that contains the word "regex" and the word "cheat":

^(?=.*regex)(?=.*cheat).*$

• Match any line that does not contain the word "Python":

^(?!.*Python).*$

• Match any line that starts and ends with the same word:

^\b(\w+)\b.*\b\1\b$

• Match any line that has more than 10 characters:

^.{11,}$

• Match any line that has exactly 3 digits:

^.*\b\d{3}\b.*$

• Match any line that has a word with 2 or more consecutive vowels:

^.*\b[aeiou]{2}\w*\b.*$

• Match any line that has a word with at least 3 consonants in a row:

^.*\b[^aeiou]{3}\w*\b.*$

• Match any line that has a word that starts with "c" and ends with "t":

^.*\bc\w*t\b.*$

Originally published on my blog at acidop.codes