Regular Expressions with re Python Tutorial

There are many times where a programmer with want to split or search in a body of text for something. Say you are looking for any prices within a body of text. Basically, you are looking for a dollar sign ($), followed by at least 1 number, maybe a decimal point, and maybe more numbers. Sometimes, there will be a decimal point before any numbers, such as with something under a dollar. Try to think of a way that you'd incorporate the very large number of possibilities, it is pretty hard. This is where regular expressions come in.

Regular expressions are used to sift through text-based data to find things. Regular expressions express a pattern of data that is to be located. Regex is its own language, and is basically the same no matter what programming language you are using with it.

In Python 3, the module to use regular expressions is re, and it must be imported to use regular expressions. Re is a part of the standard library, meaning you will not need to do any downloading and installing to use it, it is already there.

Back to our example above, before getting to the video tutorial, let me break down how prices would be discovered in a regex frame of mind:

You'd tell the regular expression module that: You are looking for the string to BEGIN with a dollar sign. Then you are either looking a group of digits, or an immediate period / decimal point. From here, you would keep looking for digits, commas, and periods until you finally reach an ending period before a space (indicating the end of a sentence rather than a decimal point), or just a space. This is exactly how you will structure a real regular expression.

For the video, our task is to locate names and ages of people. The code:

Here is a quick cheat sheet for various rules in regular expressions:


  • \d = any number
  • \D = anything but a number
  • \s = space
  • \S = anything but a space
  • \w = any letter
  • \W = anything but a letter
  • . = any character, except for a new line
  • \b = space around whole words
  • \. = period. must use backslash, because . normally means any character.


  • {1,3} = for digits, u expect 1-3 counts of digits, or "places"
  • + = match 1 or more
  • ? = match 0 or 1 repetitions.
  • * = match 0 or MORE repetitions
  • $ = matches at the end of string
  • ^ = matches start of a string
  • | = matches either/or. Example x|y = will match either x or y
  • [] = range, or "variance"
  • {x} = expect to see this amount of the preceding code.
  • {x,y} = expect to see this x-y amounts of the precedng code

White Space Charts:

  • \n = new line
  • \s = space
  • \t = tab
  • \e = escape
  • \f = form feed
  • \r = carriage return


  • . + * ? [ ] $ ^ ( ) { } | \


  • [] = quant[ia]tative = will find either quantitative, or quantatative.
  • [a-z] = return any lowercase letter a-z
  • [1-5a-qA-Z] = return all numbers 1-5, lowercase letters a-q and uppercase A-Z

The code:

So, we have the string we intend to search. We see that we have ages that are integers 2-3 numbers in length. We could also expect digits that are just 1, under 10 years old. We probably wont be seeing any digits that are 4 in length, unless we're talking about biblical times or something.

import re

exampleString = '''
Jessica is 15 years old, and Daniel is 27 years old.
Edward is 97 years old, and his grandfather, Oscar, is 102. 

Now we define the regular expression, using a simple findall method to find all examples of the pattern we specify as the first parameter within the string we specify as the second parameter.

ages = re.findall(r'\d{1,3}',exampleString)
names = re.findall(r'[A-Z][a-z]*',exampleString)


There exists 1 challenge(s) for this tutorial. for access to these, video downloads, and no ads.

There exists 1 quiz/question(s) for this tutorial. for access to these, video downloads, and no ads.

The next tutorial:

  • Python Introduction
  • Print Function and Strings
  • Math with Python
  • Variables Python Tutorial
  • While Loop Python Tutorial
  • For Loop Python Tutorial
  • If Statement Python Tutorial
  • If Else Python Tutorial
  • If Elif Else Python Tutorial
  • Functions Python Tutorial
  • Function Parameters Python Tutorial
  • Function Parameter Defaults Python Tutorial
  • Global and Local Variables Python Tutorial
  • Installing Modules Python Tutorial
  • How to download and install Python Packages and Modules with Pip
  • Common Errors Python Tutorial
  • Writing to a File Python Tutorial
  • Appending Files Python Tutorial
  • Reading from Files Python Tutorial
  • Classes Python Tutorial
  • Frequently asked Questions Python Tutorial
  • Getting User Input Python Tutorial
  • Statistics Module Python Tutorial
  • Module import Syntax Python Tutorial
  • Making your own Modules Python Tutorial
  • Python Lists vs Tuples
  • List Manipulation Python Tutorial
  • Multi-dimensional lists Python Tutorial
  • Reading CSV files in Python
  • Try and Except Error handling Python Tutorial
  • Multi-Line printing Python Tutorial
  • Python dictionaries
  • Built in functions Python Tutorial
  • OS Module Python Tutorial
  • SYS module Python Tutorial
  • Python urllib tutorial for Accessing the Internet
  • Regular Expressions with re Python Tutorial
  • How to Parse a Website with regex and urllib Python Tutorial
  • Tkinter intro
  • Tkinter buttons
  • Tkinter event handling
  • Tkinter menu bar
  • Tkinter images, text, and conclusion
  • Threading module
  • CX_Freeze Python Tutorial
  • The Subprocess Module Python Tutorial
  • Matplotlib Crash Course Python Tutorial
  • Python ftplib Tutorial
  • Sockets with Python Intro
  • Simple Port Scanner with Sockets
  • Threaded Port Scanner
  • Binding and Listening with Sockets
  • Client Server System with Sockets
  • Python 2to3 for Converting Python 2 scripts to Python 3
  • Python Pickle Module for saving Objects by serialization
  • Eval Module with Python Tutorial
  • Exec with Python Tutorial