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Lookarounds in Python

Introduction
Setting Up Your Python Environment
Installing Python and PyCharm IDE Creating and Running Your First Python Program
Python Data Types
Numeric Types String Types Boolean Types None Type
Operators and Expressions
Arithmetic Operators Comparison Operators Logical Operators Bitwise Operators Assignment Operators Operator Precedence
Control Flow Statements
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Functions and Modules
Defining and Calling Functions Function Arguments and Return Values Lambda Functions Modules and Packages
Python Data Structures
Lists Tuples Dictionaries Sets Arrays
ObjectOriented Programming in Python
Classes and Objects Attributes and Methods Inheritance and Polymorphism Abstract Classes and Interfaces
File Handling
Opening and Closing Files Reading and Writing Text Files Reading and Writing Binary Files CSV Files
Regular Expressions
Basic Regular Expressions and Metacharacters Anchors and Quantifiers Grouping and Capturing Lookarounds
Datetime and Timezones
Date and Time Objects Date and Time Formatting Timezone and Daylight Saving Time Handling
Debugging and Testing
Debugging Techniques Debugging Tools in PyCharm Unit Testing with PyTest
Web Scraping with Python
Requesting Data with urllib Parsing HTML with Beautiful Soup Extracting and Storing Data
Database Handling with Python
Connecting to Databases Performing CRUD Operations Database Access with ORM (ObjectRelational Mapping)
Introduction to Data Science with Python
NumPy Pandas Matplotlib ScikitLearn
GUI Programming with Python
Creating GUI Applications GUI Toolkits (Tkinter, PyQt, wxWidgets)
Network Programming with Python
Socket Programming Creating and Running a Simple Web Server Connecting to APIs
Best Practices and Tips
Python Coding Standards Code Organization Writing Efficient Code Tips and Tricks for Python Development
Conclusion and Next Steps.

Lookarounds

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Lookarounds refer to a concept in regular expressions in Python that allows you to look ahead or behind of a pattern without actually including it in the match. In other words, it's a way to test for a pattern match without actually consuming the characters involved.

Lookarounds are divided into two types: Positive lookaround and negative lookaround.

Positive lookaround is written as (?=pattern) or (?<=pattern), where pattern is the pattern you want to match. The first syntax is called a positive lookahead, and it matches any text that is followed by the pattern. The second syntax is called positive lookbehind, and it matches any text that is before the pattern.

Negative lookaround, on the other hand, is written as (?!pattern) or (?<!pattern). It negates the pattern match, meaning that it matches any text that is not followed or not preceded by the pattern.

Here's an example:

 
                    
import re

text = "Python is awesome!"

# Positive lookahead
result = re.search(r"Python(?= is)", text)
print(result.group()) # Output: Python

# Positive lookbehind
result = re.search(r"(?<=Python )is", text)
print(result.group()) # Output: is

# Negative lookahead
result = re.search(r"Python(?! is)", text)
print(result.group()) # Output: Python

# Negative lookbehind
result = re.search(r"(?<!awesome!)Python", text)
print(result.group()) # Output: Python

In the example above, we used lookarounds to match specific patterns in a given text without actually including them in the match. This can be particularly useful when you want to match a pattern only if it's surrounded by specific elements or substrings.

March 25, 2023

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