Complete Regular Expressions Tutorial! (with exercises for practice)

Practice your Python Pandas data science skills with problems on StrataScratch!

In this video we go through all the fundamentals of using regular expressions (regexes) to match patterns in programming.

In this video we cover the following:
- Character Sets [a-zA-Z0-9]
- Quantifiers *, +, ?, {3,5}
- Metacharacters ^ . | $
- Character Classes \b \s \w \d
- Groups
- Lookahead & Lookbehind assertions
- and more!

There is a detailed timeline down below.

In a future video we will apply what we learn in this one to the Python programming language (re library) -- subscribe to not miss that!

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Video timeline!
0:00 - Video overview & topics covered
1:43 - Basic regex syntax (building up an intuition)
4:23 - Character Sets Overview ([A-Za-z0-9])
5:57 - Quantifiers Guide (*, +, ?, {3,5})
9:30 - Guided Exercise: Find all words that don't use vowels
11:08 - Helpful cheat sheet to remember regex syntax in the real-world
12:47 - Matching words/patterns of a specific length ({3,5})
14:58 - OR operator overview
17:14 - Guided Exercise: Match valid sentences (starts with capital letter, ends with period)
21:18 - Character classes overview (\w, \b, \d, \s)
23:13 - Escaping Characters
25:02 - Practice Exercise #1: Write a regular expression to match meme text format
30:39 - Practice Exercise #2: Write a regular expression to match a specific date format
39:03 - Groups overview
50:16 - Lookahead & Lookbehind Assertions
1:00:18 - Practice Exercise #3: Detect if same word pops up multiple times in a sentence
1:06:04 - Practice Exercise #4: Password matching with rules
1:16:16 - Some final recommendations! (additional practice, chatgpt, etc.)

[Fflaring]

Oh man, I waited this so long, thank you for this video!

[Evan-e-cent]

Hi, I hope you don't mind if I comment on names for symbols:
# is called 'pound' because on British keyboards it is the money symbol £ (try option#)
! is the exclamation point or mark that you referred to later
< I call the less-than symbol or angle bracket in HTML
> is the greater than symbol (it is bigger on the left side)
* is an Asterisk which means star. Commonly called just 'star'.
| is sometimes called a pipe or vertical bar
THANKS FOR A GREAT VIDEO ! WATCHED FROM BEGINNING TO END
and made a note of the PDF cheat sheet. Very useful.

[giacomobianchi]

Finally I understood regex!!! Thank you

[stefanomedici]

Always super helpful! Thank you Keith :)

[michaelpurtell]

The legendary movie from Feb 1996 was Happy Gilmore! It surely contributed to the recent Kennedy Center honors for Adam Sandler. And a great video released on April 13, 2023 is the RegEx tutorial from Keith Galli, great job.

[ahmadshabaz]

nothing better than entire you tube . your work is awesome . its really helpful man . thanks a lots

[rayedriasat]

at 38:52 I used
here inside [ ] square brackets we don't need to escape the dot (.) it is just dot, if we had used dot outside of square brackets then we had to escape dot. Cuz dot outside [] means everything except newline

[anonviewerciv]

My body is regex. 🔎📃
10:50 Linguistically speaking, [y] can be a vowel, especially in words like "crypt". Pedantry of course, since it could just be added into the regex if needed. 🤓
36:40 Might not really be up to regex to do data validation. There are better tools for that. 🧰
In fact, integrating these into data workflows would be a good follow-up video for the future. ▶

[johnnybegood]

You are the best! Thank you for this video
props from brazil

[leonardoferreiracalazans]

Thank you for the video!

In negative lookbehind, try to use \b before the pattern you want to match. It has worked for me!

[javaluvawithjeremystones]

Really amazing video! Thanks for the great content!

For the part where it was allowing you to not escape the period in the square brackets, it's not sublime, you don't need to escape characters inside square brackets, although it won't complain if you do escape them. The only exception I can currently think of is the ^ symbol and only if you put it at the beginning.

[billsneddon]

not optimal but (0[1-9]|1[0-2]) would only match months 01-12

[shawnabirnbaum]

I would love to see a video on syntax trees and X' theory!

[maxximumb]

Ali sent me. Am so glad she did. You have some great videos.

[FUNNEAS]

Hi Keith, excellent video on regex.... One of the best videos made ever on youtube on glad i found your you make video on finding specific word in a sentence ex (i want to cancel my service. Please cancel my hbo, i want to can sail please console my service, im interested in cancelling) multiple words like this and we want to match word only (cancel | can sail |console service) and ommit any other word like 'cancel hbo' 'cancel bill' Any way can i reach out to you personally with sample. Thanks

[motlatsimoea]

Favorite tutor about to tackle a subject I've wanting to learn! Can't fight fate!

Let's

[DendrocnideMoroides]

a period in a character class only matches a period, same for the other metacharacters like ? * +, the reason for this is there is no use to have a character match every character inside a character class, since for that you would not even need a character class, similar reasoning for the other metacharacters

[JumaleAbdi-tuzh]

Hey, Thank you for the amazing content. Please Would you mind covering about End to End Pytorch series from the Problem statement, Data Collection, Modeling, Deployment, and Testing

[xjcluup]

Great video, Could you please prepare new video(tutorials) about ML?

[ucphattruong]

Omg. Thanks to you, I could understand the regex. You're truly life saver