I'm trying to do a regular expression match with special characters in it, such as "/", ".", and "-". This is the string: Show
But the following code does not seem to match at the end with :
Do I need backslash before the special characters, such as "/" and "."? Thanks! Regular expressions are a strange animal. Many students find them difficult to understand – do you? Regex Special Characters - Examples in Python Re I realized that a major reason for this is simply that they don’t understand the special regex characters. To put it differently: understand the special characters and everything else in the regex space will come much easier to you. Related article: Python Regex Superpower – The Ultimate Guide Do you want to master the regex superpower? Check out my new book The Smartest Way to Learn Regular Expressions in Python with the innovative 3-step approach for active learning: (1) study a book chapter, (2) solve a code puzzle, and (3) watch an educational chapter video. Regular expressions are built from characters. There are two types of characters: literal characters and special characters.
Literal CharactersLet’s start with the absolute first thing you need to know with regular expressions: a regular expression (short: regex) searches for a given pattern in a given string. What’s a pattern? In its most basic form, a pattern can be a literal
character. So the literal characters For example, you can search for the regex pattern Based on the simple insight that a literal character is a valid regex pattern, you’ll find that a combination of literal characters is
also a valid regex pattern. For example, the regex pattern Summary: Regular expressions are built from characters. An important class of characters are the literal characters. In principle, you can use all Unicode literal characters in your regex pattern. However, the power of regular expressions come from their abstraction capability. Instead of writing the character set So what are the special characters you can use in your regex patterns? Let’s have a look at the following table that contains all special characters in Python’s
But these are not all characters you can use in a regular expression. There are also meta characters for the regex engine that allow you to do much more powerful stuff. A good example is the asterisk operator that matches “zero or more” occurrences of the preceding regex. For example, the pattern Regex Meta CharactersFeel free to watch the short video about the most important regex meta characters: Python Regex Syntax [15-Minute Primer] Next, you’ll get a quick and dirty overview of the most important regex operations and how to use them in Python. Here are the most important regex operators:
Note that I gave the above operators some more meaningful names (in bold) so that you can immediately grasp the purpose of each regex. For example, the Let’s dive into some examples! Examplesimport re text = ''' Ha! let me see her: out, alas! he's cold: Her blood is settled, and her joints are stiff; Life and these lips have long been separated: Death lies on her like an untimely frost Upon the sweetest flower of all the field. ''' print(re.findall('.a!', text)) ''' Finds all occurrences of an arbitrary character that is followed by the character sequence 'a!'. ['Ha!'] ''' print(re.findall('is.*and', text)) ''' Finds all occurrences of the word 'is', followed by an arbitrary number of characters and the word 'and'. ['is settled, and'] ''' print(re.findall('her:?', text)) ''' Finds all occurrences of the word 'her', followed by zero or one occurrences of the colon ':'. ['her:', 'her', 'her'] ''' print(re.findall('her:+', text)) ''' Finds all occurrences of the word 'her', followed by one or more occurrences of the colon ':'. ['her:'] ''' print(re.findall('^Ha.*', text)) ''' Finds all occurrences where the string starts with the character sequence 'Ha', followed by an arbitrary number of characters except for the new-line character. Can you figure out why Python doesn't find any? [] ''' print(re.findall('\n$', text)) ''' Finds all occurrences where the new-line character '\n' occurs at the end of the string. ['\n'] ''' print(re.findall('(Life|Death)', text)) ''' Finds all occurrences of either the word 'Life' or the word 'Death'. ['Life', 'Death'] ''' In these examples,
you’ve already seen the special symbol Which Special Python Regex Characters Must Be Escaped?Short answer: Here’s an exhaustive list of all special characters that need to be escaped:
Question: Is there a comprehensive list of which special characters must be escaped in order to remove the special meaning within the regex? Example: Say you search for those symbols in a given string and you wonder which of them you must escape: |^&+-%*/=!> Answer: Differentiate between using the special symbols within or outside a character class.
import re text = '|^&+-%*/=!>' # WITHIN CHARACTER CLASS --> ESCAPE '-' print(re.findall('[|^&+\-%*/=!>]', text)) # ['|', '^', '&', '+', '-', '%', '*', '/', '=', '!', '>'] # WITHOUT CHARACTER CLASS --> ESCAPE ALL SPECIAL CHARS '.*?+^$|' pattern = '|^&+$-%*/=!>' print(re.findall('\|', text)) print(re.findall('\^', text)) print(re.findall('\$', text)) print(re.findall('\+', text)) print(re.findall('-', text)) print(re.findall('%', text)) print(re.findall('\*', text)) print(re.findall('/', text)) print(re.findall('=', text)) print(re.findall('!', text)) ''' ['|'] ['^'] ['$'] ['+'] ['-'] ['%'] ['*'] ['/'] ['='] ['!'] ''' By escaping the special regex symbols, they lose their special meaning and you can find the symbols in the original text. Where to Go From HereYou’ve learned all special characters of regular expressions, as well as meta characters. This will give you a strong basis for improving your regex skills. If you want to accelerate your skills, you need a good foundation. Check out my brand-new Python book “Python One-Liners (Amazon Link)” which boosts your skills from zero to hero—in a single line of Python code! Regex HumorWait, forgot to escape a space. Wheeeeee[taptaptap]eeeeee. (source)While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students. 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. How do you treat special characters in Python?Escape sequences allow you to include special characters in strings. To do this, simply add a backslash ( \ ) before the character you want to escape.
What does '$' mean in regex?$ means "Match the end of the string" (the position after the last character in the string).
What are the special characters in regex?Supported Special RegEx Characters. How do you check if a string contains a special character in Python?Approach : Make a regular expression(regex) object of all the special characters that we don't want, then pass a string in search method. If any one character of string is matching with regex object then search method returns a match object otherwise return None.
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