The regular expression engine will do the hard work of figuring out where the input string starts to match, and go from there. Here we are going to discuss some of the most commonly used methods and also give a few examples of how they are used. where str is the string in which we need to find the numbers. Most regular expressions are available as RegexObject methods and module-level functions. The Python regular expression library is re. Online Courses. Regular Expressions (Regex) Searching; Secure Shell Connection in Python; Security and Cryptography; Set; setup. Python Regular Expressions The regular expressions can be defined as the sequence of characters which are used to search for a pattern in a string. A regular expression is simply a sequence of characters that define a pattern. Raw Strings in Python. In the world of regular expressions, there are many different flavors to choose from, such as grep, Perl, Tcl, Python, PHP, and awk. Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript Regular Reg Expressions Ex 101. Regular Expression Examples is a list, roughly sorted by complexity, of regular expression examples. DevOps Linux. We can easily test if a string contains another string:. Basic usage of re. What are Regular Expressions. Output is not looking like a date and might need some working to change it in any format you want. Also see REGEX Column Specification below. Linux has two regular expression engines:. Written by Zeph Grunschlag. Groups are used in Python in order to reference regular expression matches. A regular expression may contain special characters that indicate that a search only matches at the beginning or end of a line or many other similar capabilities. Remember to import it at the beginning of Python code or any time IDLE is restarted. If you don’t know the basic syntax and structure of it, then it will be better to read the mentioned post. DevOps Automation. Python supports and provides a lot of methods for regular expressions and related operations. Otherwise if the match is false (None to be more specific), then the search did not succeed,. log) and since the scripts have different names but the same extension, I thought about using the regex (\w+[. You should have prior experience working with Python, should know concepts like string formats, string methods, list comprehension and so on. A regular expression can easily check whether a user entered something that looks like a valid phone number. Regular expressions (abbreviated as regex or regexp, with plural forms regexes, regexps, or regexen) are written in a formal language that can be interpreted by a regular expression processor, a program that either serves as a parser generator or examines text and identifies parts that match the provided specification. It is common to use the 'r' at the start of the pattern string, that designates a python "raw" string which passes through backslashes without change which is very handy for regular expressions. Python provides support for regular expressions via re module. When programmers write regular expressions in Python, they begin raw strings with a special prefix 'r' and backslashes and special meta-characters in the string, that allows us to pass through them to regular-expression-engine directly. Here are some important topics: 1. How do I use the grep command with regular expressions on a Linux and Unix-like operating systems? How do I use grep and regular expressions to search for text/ words in Linux? Linux comes with GNU grep, which supports extended regular expressions. Python - 25 Python interview questions and 86 answers by expert members with experience in Python subject. It allows you to iterate over each line in a csv file and gives you a list of items on that row. You don't actually need regular expressions for an exact string match in Python. The term "regular expression", sometimes also called regex or regexp, is originated in theoretical computer science. The Java Matcher class (java. Built with love by Steven Wade using VerbalExpressions. net In the last post (Beginner’s Guide to Python Regular Expression), we learnt about python regular expression. ※ Refer the regular expression grammar here. The Regex Library contains complete examples that can be conveniently pasted into the Kodos main window and can be customized to meet the goals of the user. The example also shows how to make Java regular expression case insensitive using (?i) modifier as well as Pattern class. For example, let's say you are tasked with finding the number of punctuations in a particular piece of text. You can see the using of a separator, dictionaries, split only on first separator or how to treat consecutive separators. This is of the form NAME := expr where expr is any valid Python expression other than an unparenthesized tuple, and NAME is an identifier. Let's say we have a regular expression that has 3 subexpressions. Python Regular Expression Example. Kodos - Help. Python Regular Expression Tutorial - A regular expression in python, is simply a special sequence of characters, helps you to match the other set of strings, using specialized syntax, in a pattern. This book covers both re module and the third-party regex module. sub() method. I am learning regex in php but want to try out how the regex in python works. You can vote up the examples you like or vote down the ones you don't like. This is called a substring match, instead, and can be accomplished with the `in` operator, because strings are just special sequences (lists): [code] if 's' in 'strin. You’ll usually be able to access this data in csv format, or via an Application Programming Interface (API). You don't actually need regular expressions for an exact string match in Python. We need special characters which a specific mean in the context of regular expressions. The endswith method does not allow for a regular expression. NET Framework programming. All I've done is translate the code from Perl to Python 2. In Python you need the re module for regular expressions usage. Regular Expressions Cheat Sheet for Python, PHP, Perl, JavaScript and Ruby developers. The next two columns work hand in hand: the "Example" column gives a valid regular expression that uses the element, and the "Sample Match" column presents a text string that could be matched by the regular expression. A regular expression, regex or regexp (sometimes called a rational expression) is a sequence of characters that define a search pattern. It is used in Lybniz evaluate the functions input by the user. Myregextester. group() is the matching text (e. RE module methods: search(). Regular expression matching with Python and biopython SeqIO. group() would result in a AttributeError: exception. Python Regular Expression. There are several good places to look. NOTES '\' character in a string must itself be escaped. They are often used to perform searches, replace substrings and validate string data. The thing is the ^about/ regular expression simply says 'match anything that begins with about/', therefore a request made for the /about/index url produces a match, so you must be very careful when using re_path statements to declare more granular url regular expressions towards the top and broader url regular expressions towards the bottom. match() is. Example pattern: one or more. Write a Python program to find urls in a string. But sometimes we have the condition that this pattern is preceded or followed by another certain pattern. split" function and at the same time we have used expression \s that allows to parse each word in the string separately. But I'm looking for a way to copy only the marked text (or the text that matches the regex expression). Key techniques used in crafting each regex are explained, with links to the corresponding pages in the tutorial where these concepts and techniques are explained in great detail. To understand how this regular expression works in Python, we begin with a simple example of a split function. The Java Regex or Regular Expression is an API to define a pattern for searching or manipulating strings. Complete understanding of Regular Expressions and how to use RE module in Python programming. com · 3 Comments It is not uncommon for us to need to extract text from a PDF. There is an optional argument called sep, short for separator, that you can use to change that space to something else. This section will cover some of Python's built-in string methods and formatting operations, before moving on to a quick guide to the extremely useful subject of regular expressions. Getting Started 1 Installing Python on Mac 2 Installing Python on Windows. Summary of Regular Expression Syntax ¶ The table below contains some commonly used and basic rule/sytnax used to construct regular expressions (RE). Python Regular Expression. The following line of code is necessary to include at the top of your code: import re. For example a host name might be T1234SWT0001 and I'd like to capture any device with "T" + "four digits" + "SWT" + "anything". To understand how this regular expression works in Python, we begin with a simple example of a split function. ''' import argparse import re from pycallgraph import PyCallGraph from pycallgraph import Config from pycallgraph. If you print the output of re. While it may sound fairly trivial to achieve such functionalities it is much simpler if we use the power of Python's regex module. Python regex python text camlcase saved by 1 person posted on January 19, 2011 by jarnaldich; Python: simple REgex example Python regex re saved by 1 person posted on January 17, 2010 by magicrebirth; python script to extract all email addresses from bulk text Python regex email python script regular Expression saved by 1 person. Python regular expression module can be used to replace a pattern in a string using re. Regular Expression By Example. They are used to test strict grammar rules on a string. In JavaScript, regular expressions are also objects. Regular Expression Syntax. Followers 0. Regular expressions allow one to use pattern matching on objects. Some of the features described here may not be available in earlier versions of Python. Note The System. Web Scraping Reference: A Simple Cheat Sheet for Web Scraping with Python October 24, 2018 Once you’ve put together enough web scrapers, you start to feel like you can do it in your sleep. Python provides the csv module for parsing comma separated value files. Python's built-in "re" module provides excellent support for regular expressions, with a modern and complete regex flavor. Characters can be listed individually, or a range of characters can be indicated by giving two characters and separating them by a '-'. you should always try to take Online Classes or Online Courses rather than Udemy Python Regular Expressions With Examples Download, as we update lots of resources every now and then. ]py) to identify all the python logs. For example, the Hello World regex matches the "Hello World" string. Python Regex - Check if String starts with Specific Word; Python Regex - Check if String ends with Specific Word. How to Parse a Website with regex and urllib Python Tutorial In this video, we use two of Python 3's standard library modules, re and urllib, to parse paragraph data from a website. Item 23: Character class. Here is some common used flags in python applications. See issue 3262. The question mark, for example, says that the preceding expression (the character “a” in this case) may or may not be present. A regular expression is a special sequence of characters that helps you match or find other strings or sets of strings, using a specialized syntax held in a pattern. While using the regular expression, the first thing is to recognize that everything is essentially a character, and we are writing the patterns to match the specific sequence of characters also referred to as a string. A regular expression is that a set of possible input raw strings (includes alphanumerical, whitespaces, symbols). findall, which will return a list of tuples, or re. 1 Regular expression examples for decimals. Chapter 11 Regular expressions So far we have been reading through files, looking for patterns and extracting various bits of lines that we find interesting. Some recent studies estimate that between 100 to 150 million computers worldwide would be directly infected by at least one malware such as Trojan or Keylogger in order to be remotely monitored or controlled by hackers. Oracle has long supported the ANSI-standard LIKE predicate for rudimentary pattern matching, but regular expressions take pattern matching to a new level. A quick reference guide for regular expressions (regex), including symbols, ranges, grouping, assertions and some sample patterns to get you started. Also, you will learn to convert JSON to dict and pretty print it. Summary of Regular Expression Syntax ¶ The table below contains some commonly used and basic rule/sytnax used to construct regular expressions (RE). This tutorial is a gentle introduction to getting you started with using regular expressions in calibre. This section will cover some of Python's built-in string methods and formatting operations, before moving on to a quick guide to the extremely useful subject of regular expressions. The so-called special characters are characters with special meanings, such as * in “*. While at Dataquest we advocate getting used to consulting the Python documentation , sometimes it's nice to have a handy PDF reference, so we've put together this Python regular expressions (regex. (NEED EXAMPLE) If a group is contained in a part of the pattern that matched multiple times, the last match is returned. It also includes usage of regex using various tools such as R and Python. A regular expression is a special text string for describing a search pattern. Regex with NLTK tokenization Twitter is a frequently used source for NLP text and tasks. This project tries to provide many snippets of Python code that make life easier. When you want to match a string to perhaps validate an email or password, or even extract some data, a regex is an indispensable tool. Python will insert a space between each of the arguments of the print function. Example: The regex "aa " tries to match two consecutive "a"s at the end of a line, inclusive the newline character itself. The first example of a metaclass is taken from the Python standard library. In order to make python regular expressions can match string on multi-lines and case-insensitive, we should use regular expression flags. As you can see, in this example we are going to use a text present in Gutenberg corpus. About regular expressions in egrep. In the first article of this series, we will focus on discussing. Leetcode (Python): Best Time to Buy and Sell Stock Leetcode: Best Time to Buy and Sell Stock II Leetcode (Python): Minimum Path Sum Leetcode (Python): Validate Binary Search Tree Leetcode: Validate Binary Search Tree Leetcode (Python): Regular Expression Matching Leetcode (Python): Binary Tree Zigzag Level Order. In this article, we show how to use named groups with regular expressions in Python. Parsing URLs with Regular Expressions and the Regex Object - Cambia Research. Python Programming Courses & Exercises; Sometimes Regular Expressions are called regex or regexp. For example, let's say you are tasked with finding the number of punctuations in a particular piece of text. To do this, we first need a fancier tokenizer. The reason I check if the length of "email" is greater than 7 is because to the best of my knowledge, no address can be shorter than 7 characters (ie. 35+ Examples of Regex Patterns Using sed and awk in Linux In this article, we go through a lot of great ways to use Regular Expression, or Regex, Patters, and their applications in sed and awk. sub, so you can use exactly same regular expressions you would use for re. A match object in RegEx is an object containing information about the search and the result. You can also use a Matcher to search for the same regular expression in different texts. For example, let's say you are tasked with finding the number of punctuations in a particular piece of text. We would cover two important functions, which would be used to handle regular expressions. UUID regular expressions (regex) with usage examples in Python - uuid_regex. " Wondering how to use regular expressions for address validation? We get a lot of questions from programmers about parsing and validating addresses. Can I Use a Regular Expression with Python startswith()? No. Python's Hidden Regular Expression Gems. A ‘regular expression’ is a pattern that describes a set of strings. (NEED EXAMPLE) If a group is contained in a part of the pattern that matched multiple times, the last match is returned. ' special character does not match newline characters. Support for regular expressions in SQL and PL/SQL is one of the most exciting features of Oracle Database 10G. After many years of using Perl I am starting to learn Python. Another good use of regular expressions in bash commands could be redacting emails within a text file. >>> line1="qwerty asdf zxcv poiu mnba" >>> regex=r'([a-zA-Z0-9]* )' >>> matches = re. Here are some examples using grep: Text version. [24] The match() method looks for zero or more characters at the beginning of the given string that match the given regular expression and returns a match object if found, or None if there is no match. Python Regular Expression. Here are some important topics: 1. We cover Python methods (like re. Examples are used extensively, please follow along by typing them out. Or simply, I want to extract every piece of text inside the [p][/p] tags. sub(‘Python’, ‘Regex is excellent’) will return the string, Python is excellent. So, I'm going to write what I've learned! In this blog post I am going to: Explain what a regular expression is. What is a Regular Expression? It's a string pattern written in a compact syntax, that allows us to quickly check whether a given string matches or contains a given pattern. course gives you comprehensive overview of Python's RE module. To manipulate strings and character values, python has several in-built functions. you should always try to take Online Classes or Online Courses rather than Udemy Python Regular Expressions With Examples Download, as we update lots of resources every now and then. In this post you can find useful information for beginers and advanced how to split strings into lists. The Python2orPython3 page provides advice on how to decide which one will best suit your needs. Python Regular Expression is one of my favourite topics. For example, what if later you wanted to change it to printing something like "The regex is valid? {}". We need special characters which a specific mean in the context of regular expressions. What are Regular Expressions. Writing regular expression patterns using: Repetitions; Non Greedy Repetitions; Character Sets. Here, we will discuss Metacharacters, examples & functions of Python Regex. The search pattern is defined by regular expression. py; shelve; Similarities in syntax, Differences in meaning: Python vs. Python, Perl, Java, SED, AWK and even X#. A simple example for a regular expression is a (literal) string. Here are some important topics:. The flags modifies the meaning of the given regex pattern. UUID regular expressions (regex) with usage examples in Python - uuid_regex. String escapes 62 For example, the regex r[ea]d matches both red and rad ar, but not read. Now available for Python 3!. Regular Expressions in Python Published Jan 19, 2019 Last updated Jun 05, 2019 Regular Expressions are a sequence of characters used to find and replace patterns in a string In simple terms it is a tool for matching patterns in text. DevOps Automation. Let's say we have the following string in Python, shown below:. # Create a test string replace_me = " Replace bird with a duck " # Create an expression that looks for the word "bird" expression = VerEx(). You can do a whole lot more with the Matcher class. ) and Linux programs like (sed, awk, grep) and many other applications. Regular expressions can be as simple as plain text, or use a unique language consisting of special characters and modifiers to build these patterns. This tutorial covers various concepts of regular expression (regex) with hands-on examples. Hence, in this Python Unittest tutorial, we discussed Unit Testing with Python. By Alex Yang, Dataquest. The 'search' method is the main way to use regular expressions in your pattern matching: import re tree=get_name(1) if re. A language for expressing more complex search strings. This is a tale of two approaches to regular expression matching. Other languages, such as C, C++, and Python supports regular expressions through extension libraries. Groups are used in Python in order to reference regular expression matches. GNU grep is the default on all Linux systems. provide support for string manipulation using regular expressions. RE module methods: search(). match, the pattern must match the beginning of the string. The difference between stemming and lemmatization is, lemmatization considers the context and converts the word to its meaningful base form, whereas stemming just removes the last few characters, often leading to incorrect meanings and spelling errors. Item 23: Character class. That means: When regex matches, emit a token with the match text and type tokentype and push new_state on the state stack. Regular expressions are extremely useful for preprocessing text that can be further used for a variety of applications, such as topic modeling, text classification, sentimental analysis, and text summarization, etc. Here are some important topics: What are Regular Expressions. Python Regex Tutorial. Also see REGEX Column Specification below. group() would result in a AttributeError: exception. search Regular Expression In Python For E-Mail And Phone Number. Regular expressions are extremely useful for matching common patterns. Python print command operators The print statement is useful for joining multiple words, strings, num bers with different data types as well. Python Regular Expression is one of my favourite topics. Regular expressions (REs, or regexes, or regex patterns) are used to identify whether a pattern exists in a given sequence of strings or not. Regular Expression Basics. After all, 'HaHaHa' and 'HaHaHaHa' are also valid matches of the regular expression (Ha){3,5}. The course goals are: Teach you how to use the Python regular expressions (re) module and relevant functions by running interactive examples;. This method returns a match object in case there was a match, or None if there was no match. net This examples also show the strength of python regular expression in information retrieval from unstructured data. A language for expressing more complex search strings. A great thing about regular expressions: The syntax of regular expressions is the same for all programming and script languages, e. Python regex flags effect matching. Returns the full name of the series with the separator needed to make it pretty (ie, replace it with space or what you want). Let’s see how to Replace a pattern of substring with another substring using regular expression. findall (para) Above code will extract all of the characters and display it. You should have prior experience working with Python, should know concepts like string formats, string methods, list comprehension and so on. We'll also experience how efficiently regex and the pandas library bring order to large, unorganised data sets. Example Problem: Converting Date and Time: Without using library functions, we want a Python program that will convert an "American Style" time and date to the corresponding "International Style. We will also learn about the match and search functions, along with special sequence characters and regular expression modifiers. Feel free to contribute!. Python Regex - Check if String starts with Specific Word; Python Regex - Check if String ends with Specific Word. Start studying Python and Regular Expressions. Learn Python online: Python tutorials for developers of all skill levels, Python books and courses, Python news, code examples, articles, and more. Here we are going to discuss some of the most commonly used methods and also give a few examples of how they are used. In the first part of this series, we looked at the basic syntax of regular expressions and some simple examples. First, let's understand the terms, greedy and lazy matching. format(ans) In that case you would have to update 2 locations (and would likely miss the exception case if you were in a hurry). A regular expression, regex or regexp (sometimes called a rational expression) is a sequence of characters that define a search pattern. The Regex Library contains complete examples that can be conveniently pasted into the Kodos main window and can be customized to meet the goals of the user. Some basic programming skills in Python. where str is the string in which we need to find the numbers. Groups are used in Python in order to reference regular expression matches. However, its only one of the many places you can find regular expressions. Unfortunately, passing these flags is awkward if want to put regex patterns in a config file or database or otherwise want to have the user be able to enter in regex patterns. From 2006-2016, Google Code Project Hosting offered a free collaborative development environment for open source projects. Regular expressions are essentially a highly specialized programming language embedded inside Python that empowers you to specify the rules for the set of possible strings that you want to match. A s a simple example, let's use it to duplicate the functionality of the string split() method. Basic usage of re. Regular expressions can be as simple as plain text, or use a unique language consisting of special characters and modifiers to build these patterns. What follows is a brief explanation of the math for why that is. It is common to use the 'r' at the start of the pattern string, that designates a python "raw" string which passes through backslashes without change which is very handy for regular expressions. course gives you comprehensive overview of Python's RE module. Python's built-in "re" module provides excellent support for regular expressions, with a modern and complete regex flavor. Validate ZIP Codes Problem You need to validate a ZIP code (U. findall() returns list of strings that are matched with the regular expression. Related course: Complete Python Programming Course & Exercises. Use this code --> Import re. Go in depth in understanding the structure of a URL or URI and see a single regular expression that can be used to extract the various pieces in one fell swoop. RE Module Functions. The code also gives an example of a function within a function. Regular Expressions are used in programming languages to filter texts or textstrings. Or simply, I want to extract every piece of text inside the [p][/p] tags. Regex with NLTK tokenization Twitter is a frequently used source for NLP text and tasks. Python's regular expressions are greedy by default, which means that in ambiguous situations they will match the longest string possible. Usually such patterns are used by string searching algorithms for "find" or "find and replace" operations on strings, or for input validation. Given a string, write a Python program to check whether the given string is ending with only alphanumeric character or Not. We are comparing descriptions on a bank statement and we need to say for one account: If the description matches "BBM TFR TO 20-24-61" then it is this category, otherwise it is another category. pysheeet website; pysheeet @ GitHub; Issue Tracker; pysheeet as a PDF; Table of Contents. To use regular expressions in python, you must import the regular expression module with import re. For more information, read this fantastic article. Python can be used for web scraping, web development, image processing, analyzing data, working with regular expressions, automation, etc. In Python, we have module “re” that helps with regular expressions. Write a Python program to find urls in a string. To work around that you can use a raw string, by prefixing the string with the letter r. For example, you want to send a reminder to your customers for their remaining bills and you have all customer related data like their phone numbers, address, age etc in an excel sheet or a database then instead of doing it manually, you can write a simple program in Python to automatically do that for you. "alexa?" Some characters have special meanings in a regular expression. By solving these exercises, you will be able to write regular expressions for different kinds of text data. The search and replacement is done using Python's regular expression module re. py), indispensible when trying out regular expressions; ships with PythonCard as well. The following are code examples for showing how to use re. A Re gular Ex pression (RegEx) is a sequence of characters that defines a search pattern. 6/Boolean Expressions. Useful Links. a string which is designed to match a particular type of strings. the Stack Overflow. Python Regex - Check if String starts with Specific Word; Python Regex - Check if String ends with Specific Word. Most programming languages have a split() function that takes a regular expression and a string. 1 Regex Examples (PCRE) 1. In this tutorial you will learn how to create log file parser in python. What you'll learn Complete understanding of Regular Expressions and how to use RE module in Python programming. Python Regular Expression Tutorial Discover Python regular expressions: find basic and complex patterns, repetitions, or to do (non-)greedy matching, work with the re library and much more! Regular expressions are used to identify whether a pattern exists in a given sequence of characters (string) or not. The flags can be any of: Summary of Regex Flags syntax long syntax meaning re. Many basic patterns can be easily tackled using these special characters. Regular expressions are used to sift through text-based data to find things. Regex Pattern for Parsing CSV files with Embedded commas, double quotes and line breaks Tuesday, October 14, 2008 at 5:32AM While you have stumbled on KimGentes. A Re gular Ex pression (RegEx) is a sequence of characters that defines a search pattern. Some of the features described here may not be available in earlier versions of Python. The findall method expects a regular expression as its parameter but its regular expression is a bit different from the normal regular expression. Examples are used extensively, please follow along by typing them out. sub(‘Python’, ‘Regex is excellent’) will return the string, Python is excellent. Learn vocabulary, terms, and more with flashcards, games, and other study tools. There are many different applications use different types of regex in Linux, like the regex included in programming languages (Java, Perl, Python,,,) and Linux programs like (sed, awk, grep,) and many other applications. Sometimes we need to look if a string matches or contains a certain pattern and that's what regular expressions (regex) are for. The regex object can then be used to search for approximate matches using its search () method. Python Regular Expression Tutorial - A regular expression in python, is simply a special sequence of characters, helps you to match the other set of strings, using specialized syntax, in a pattern. Using this little language, you specify the rules for the set of possible strings that you want to match; this set might contain English sentences, or e-mail addresses, or TeX commands, or anything you like. Regular expressions are used for text searching and more advanced text manipulation. Python Examples Even More Examples Urls:. The search pattern is defined by regular expression. The question mark, for example, says that the preceding expression (the character “a” in this case) may or may not be present. Then the matches () method is called on the Matcher instance. regex API and presents several working examples to illustrate how the various objects interact. py, and accessed using import re. Python has built-in support for regular function. The rest is covered throughout the rest of this tutorial. The sections below include examples of using the field calculator. 10-digit phone number with hyphens match whole word Find Substring within a string that begins and ends with paranthesis Simple date dd/mm/yyyy all. There are many different applications use different types of regex in Linux, like the regex included in programming languages (Java, Perl, Python,,,) and Linux programs like (sed, awk, grep,) and many other applications. Web Scraping Reference: A Simple Cheat Sheet for Web Scraping with Python October 24, 2018 Once you’ve put together enough web scrapers, you start to feel like you can do it in your sleep. Usage examples for regular expressions in Python. The following are code examples for showing how to use re. In most contexts where arbitrary Python expressions can be used, a named expression can appear. While it may sound fairly trivial to achieve such functionalities it is much simpler if we use the power of Python’s regex module. This is of the form NAME := expr where expr is any valid Python expression other than an unparenthesized tuple, and NAME is an identifier. Many of you do not find this combination easy, which partly happens because of the Python's obfuscated regex documentation too! In this course, to make your life easy, I have used some real-world examples. Example 2: The period: According to Python's regular expression documentation, the period matches any character except a newline. For example, the Hello World regex matches the "Hello World" string. match (r 'dogs', line, re.