Need a little extra help with those Regular Expression(regex) functions? Then look no further! Here, I have put together the best top 10 regex cheat sheets for you to download, print and pin to the bathroom wall!!
- Python Regex Cheat Sheet Examples Download
- Python Regex Cheat Sheet Pdf
- How To Use Regex In Python
- C# Regex Cheat Sheet
- Regex Cheat Sheet Php
This cheat sheets will be a great reference when you need to put them in your scripts when you are web scraping and trying to find information or when you need help to authenticate users and passwords!
Can You Use a Regular Expression with the Python startswith Method? The startswith method does not allow for a regular expressions. You can only search for a string. A regular expression can describe an infinite set of matching strings. For example, 'A.' matches all words starting with 'A'. This can be computationally expensive. RegExes syntax can be hard to recall. Check out our “Python RegEx Cheatsheet” to help point you in the right direction when building RegExes in Python.
Regular Expressions Cheat Sheet for Python, PHP, Perl, JavaScript and Ruby developers. The list of the most important metacharacters you'll ever need.
All the regex cheat sheets in this article are 100% free. All links open a new tab (feel free to open all the links without losing this page!)
This cheat sheet is based on Python 3’s documentation on regular expressions. If you're interested in learning Python, we have a free Python Programming: Beginner course for you to try out. Download the cheat sheet here. Special Characters ^ Matches the expression to its right at the start of a string. Pythex is a real-time regular expression editor for Python, a quick way to test your regular expressions.
Cheat Sheet 1: Rexegg.com
This first sheet is from Rexegg.com. The entire list is one that is commonly used Regex expressions in Python and other languages. This list includes Characters, Quantifiers and more. It will even tell you what language this expression can be used in! This makes it a lot easier when you go to write a regex in your language preference. This website really does emphasize looking at the tables for the expressions by keeping the tables bright on a black background. Making it easy to read the table but very difficult to read the information on regex itself.
Pros: Tables are bright and easy to read. Contains a lot of information shorthand to write regex
Cons: Information on the page is very dark and difficult to read.
Cheat Sheet 2: Regular Expressions cheat sheet – MIT
This second sheet was written by MIT. It is very spartan with no color and straight to the point on what the expressions are and what they do. This is the perfect cheat sheet if you do not want to be distracted by color or graphics. However, since it is very dry in the manner of text, I would not suggest this particular cheat sheet to someone who is just learning regular expressions since the explanations and examples are minimal.
Pros: Clean text, no colors for distraction, contains a lot of information shorthand to write regex
Cons: Too spartan for a total beginner in Regex
Cheat Sheet 3: Cheatography.com
I really love this website! This sheet was put together by Dave Child for regular expressions. It’s a nice quick reference guide pdf you can print in bright pink. It is easy to read and rated ‘E’ for everyone! It includes symbols, ranges, grouping, assertions and more with sample patterns to help get you on your way! Cheatography is one of my favorite websites for cheat sheet because they have so many on so many different topics and in many styles. It’s nice to find a one stop shop for cheat sheets.
Pros: Explains regex easily, uses soft colors, contains a lot of information.
Cons: Color may be distracting to some.
Cheat Sheet 4: Dev.to
Dev.to is a great place for new and experienced developers! This regex list was written by Catherine on her dev.to profile where she explains regex expressions in Java-script she has compiled with her resources at the bottom of here article.
Pros: Great spot to read someone else’s experience in regex and to gather new resources
Cons: More of an article than an actual pdf to print.
Cheat Sheet 5: Last Call – The Rapid API Blog
This is another great website for developers! This cheat sheet is also very easy to read and understand. It has additional resources beneath the code written. There are no examples in the post but there is shorthand explanations for each expression, characters and quantifiers. I would not suggest this particular cheat sheet for a beginner.
Pros: Great for those who understand regex and don’t have a need for examples
Cons: Not for Beginners since it has minimal explanation
Cheat Sheet 6: GREP
Here is another one! This one is minimal in color to keep distractions down. Key words are in red and examples are done in yellow. There are minimal explanations in the color keys. This sheet is for the advanced regex user who only needs a quick reference. It is clean and easy to read. It covers all of the information needed to write your own regex!
Pros: Written cleanly, additional resources at the bottom, to the point.
Cons: Not for the regex beginner.
Cheat Sheet 7: Regex chart
This Regex sheet is a very quick one with only the characters, the meaning and an example. This one is also for the advanced regex user. There is only the bare minimum here and this particular sheet does not contain quantifiers or expressions. There is a link however to a regex character classes cheat sheet.
Pros: Very quick reference of only character in regex
Cons: Not for a beginner regex user.
Cheat Sheet 8: Keycdn
Here is another awesome website to learn Regular expressions from! It goes over what regex is, gives you the list of expressions and gives you 2 separate examples on how regex is used in find numbers and emails. Near the bottom it even give you 3 tools to help you learn how to build a proper regex formula! These test sites will help you not only to build regex but compile it and make sure it running correctly before implementing it into your code.
Pros: Not only information but tools as well!
Cons: none as far I can see.
Cheat Sheet 9: MDN Web Docs
This regex syntax cheat sheet is on one of my absolute favorite places to learn about web development!! Named Moz:a (pronounced Mozilla) this particular guide will walk through not only the syntax but take you to the complete guide on regex! This cheat sheet is rated ‘E’ for everyone! It has clear examples and explanations on beginner and advanced regex characters and expressions.
Pros: Great for Everyone!!
Cons: N/A
Cheat Sheet 10: Dataquest
The final cheat sheet!! This final cheat sheet is from Dataquest. This particular cheat sheet was written specifically for Python!! This pdf is downloadable for free and explains each character and expression in detail. There is a lot of information packed in this pdf each under the proper heading and minimal color for the least number of distractions.
Pros: A lot of information pack in with minimal color.
Cons: Can appear to be overwhelming at first glance to a beginner.
I would like to thank you for taking the time to read this article. I hope that you are able to use at least one of these cheat sheets the next time you need to put a regular expression in your coding! The best way to learn though is to practice!! Good luck with writing your regex!!
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I’m sitting in front of my computer refactoring Python code and have just thought of the following question:
Can You Use a Regular Expression with the Python string.startswith() Method?
The short answer is no. The string.startswith() method doesn’t allow regular expression inputs. And you don’t need it because regular expressions can already check if a string starts with a pattern using the re.match(pattern, string) function from the re module.
In fact, shortly after asking the question, I realized that using a regex with the startswith() methoddoesn’t make sense. Why? If you want to use regular expressions, use the re module. Regular expressions are infinitely more powerful than the startswith() method!
For example, to check whether a string starts with 'hello', you’d use the regex 'hello.*'. Now you don’t need the startswith() method anymore because the regex already takes care of that.
If you already learned something from this tutorial, why not joining my free Python training program? I call it the Finxter Email Computer Science Academy—and it’s just that: a free, easy-to-use email academy that teaches you Python in small daily doses for beginners and pros alike!
How Does the Python startswith() Method Work?
Here’s an overview of the string.startswith() method:
Let’s look at some examples using the Python startswith() method. In each one, I will modify the code to show different use cases. Let’s start with the most basic scenario.
Related article:Python Regex Superpower – The Ultimate Guide
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Python startswith() — Most Basic Example
Suppose you have a list of strings where each string is a tweet.
Let’s say you work in the coffee industry and you want to get all tweets that start with the string 'coffee'. We’ll use the startswith() method with a single argument:
There is only one tweet in our dataset that starts with the string 'coffee'. So that is the only one printed out.
Python startswith() — Optional Arguments
The startswith() method has two optional arguments: start and end. You can use these to define a range of indices to check. By default startswith checks the entire string. Let’s look at some examples.
The start argument tells startswith() where to begin searching. The default value is 0 i.e. it begins at the start of the string. So, the following code outputs the same result as above:
What happens if we set start=7?
Why does it print 'i like coffee'? By calling the find() method, we see that the substring 'coffee' begins at index 7.
Hence, when checking tweet.startswith('coffee', 7) for the tweet 'i like coffee', the result is True.
Let’s add another argument – the end index – to the last snippet:
Nothing is printed to the console. This is because we are only searching over 2 characters – beginning from index 7 (inclusive) and ending at index 9 (exclusive). But we are searching for ‘coffee’ and it is 6 characters long. As 6 > 2, startswith() doesn’t find any matches and so returns nothing.
Now that you know everything about Python’s startswith method, let’s go back to our original question:
Can You Use a Regular Expression with the Python startswith() Method?
No. The startswith method does not allow for a regular expressions. You can only search for a string.
A regular expression can describe an infinite set of matching strings. For example, 'A*' matches all words starting with 'A'. This can be computationally expensive. So, for performance reasons, it makes sense that startswith() doesn’t accept regular expressions.
Instead, you can use the re.match() method:
re.match()
The re.match(pattern, string) method returns a match object if the pattern matches at the beginning of the string. The match object contains useful information such as the matching groups and the matching positions. An optional argument flags allows you to customize the regex engine, for example to ignore capitalization.
Specification: re.match(pattern, string, flags=0)
The re.match() method has up to three arguments.
pattern: the regular expression pattern that you want to match.string: the string which you want to search for the pattern.flags(optional argument): a more advanced modifier that allows you to customize the behavior of the function. Want to know how to use those flags? Check out this detailed article on the Finxter blog.
Return Value:
The re.match() method returns a match object. You can learn everything about match objects and the re.match() method in my detailed blog guide:
Here’s the video in case you’re more the multimodal learner:
But is it also true that startswith only accepts a single string as argument? Not at all. It is possible to do the following:
Python startswith() Tuple – Check For Multiple Strings
This snippet prints all strings that start with either 'coffee' or 'i'. It is pretty efficient too. Unfortunately, you can only check a finite set of arguments. If you need to check an infinite set, you cannot use this method.
What Happens If I Pass A Regular Expression To startswith()?
Let’s check whether a tweet starts with any version of the 'coffee' string. In other words, we want to apply the regex 'coff*' so that we match strings like 'coffee', 'coffees' and 'coffe'.
This doesn’t work. In regular expressions, * is a wildcard and represents any character. But in the startswith() method, it just means the star character '*'. Since none of the tweets start with the literal string 'coff*', Python prints nothing to the screen.
So you might ask:
What Are The Alternatives to Using Regular Expressions in startswith()?
There is one alternative that is simple and clean: use the re module. This is Python’s built-in module built to work with regular expressions.
Success! We’ve now printed all the tweets we expected. That is, all tweets that start with “coff” plus an arbitrary number of characters.
Note that this method is quite slow. Evaluating regular expressions is an expensive operation. But the clarity of the code has improved and we got the result we wanted. Slow and successful is better than fast and unsuccessful.
The function re.match() takes two arguments. First, the regular expression to be matched. Second, the string you want to search. If a matching substring is found, it returns True. If not, it returns False. In this case, it returns False for “to thine own self be true” and True for the rest.
So let’s summarize the article.
Summary: Can You Use a Regular Expression with the Python startswith Method?
No, you cannot use a regular expression with the Python startswith function. But you can use the Python regular expression module re instead. It’s as simple as calling the function re.match(s1, s2). This finds the regular expression s1 in the string s2.
Python Startswith() List
Given that we can pass a tuple to startswith(), what happens if we pass a list?
Python Regex Cheat Sheet Examples Download
Python raises a TypeError. We can only pass a tuple to startswith(). So if we have a list of prefixes we want to check, we can call tuple() before passing it to startswith.
This works well and is fine performance wise. Yet, one of Python’s key features is its flexibility. So is it possible to get the same outcome without changing our list of letters to a tuple? Of course it is!
We have two options:
- any + list comprehension
- any + map
The any() function is a way to combine logical or statements together. It takes one argument – an iterable of conditional statements. So instead of writing
We write
This is much nicer to read and is especially useful if you are using many mathematical statements. We can improve this by first creating a list of conditions and passing this to any().
Alternatively, we can use map instead of a list comprehension
Both have the same outcome. We personally prefer list comprehensions and think they are more readable. But choose whichever you prefer.
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Python Regex Course
Google engineers are regular expression masters. The Google search engine is a massive text-processing engine that extracts value from trillions of webpages.
Mac keystroke for paste text only. Facebook engineers are regular expression masters. Social networks like Facebook, WhatsApp, and Instagram connect humans via text messages.
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Amazon engineers are regular expression masters. Ecommerce giants ship products based on textual product descriptions. Bank gothic font free download. Regular expressions rule the game when text processing meets computer science.
If you want to become a regular expression master too, check out the most comprehensive Python regex course on the planet:
While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.
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To help students reach higher levels of Python success, he founded the programming education website Finxter.com. He’s author of the popular programming book Python One-Liners (NoStarch 2020), coauthor of the Coffee Break Python series of self-published books, computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.
His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.
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