Regex en 5 minutos

A regular expression is a tiny pattern language for matching text. Instead of one fixed word, you describe the shape of what you want to find.

Python uses the built-in re module for regex. Import it once and you can search, match, and extract patterns from any string.

The simplest pattern is a literal. The pattern dog matches the exact letters d, o, g, in that order, wherever they appear in your text.

Use re.search to scan a string and return the first place your pattern appears, or None when nothing matches at all.

A character class in square brackets matches any one listed character. The pattern [abc] matches a single a, b, or c each time.

Some classes have shortcuts. \d matches any digit, \w matches word characters, and \s matches spaces. They save you a lot of typing. 😊

The dot stands for any single character except a newline. So h.t matches hat, hit, and hot, but never the two-letter ht.

A quantifier says how many times the part before it repeats. Add a plus for one or more, a star for zero or more.

Use braces for precise repetition. The pattern \d{3} matches exactly three digits in a row, perfect for area codes or short IDs.

Anchors match a position, not a character. The caret means start of string and the dollar sign means end of string.

While search finds one match, re.findall returns a list of every match in the text, which is great for counting or extracting many items.

You want to match exactly three digits in a row. Which pattern fits?

You met literals, classes, the dot, quantifiers, and anchors. With re.search and re.findall, you can already describe and find real patterns. 🎉