Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How does nested character class subtraction work in Python?
Nested Character Class Subtraction
Since we can use the full character class syntax within the subtracted character class, we can subtract a class from the class being subtracted. [0-9-[0-7-[0-3]]] first subtracts 0-3 from 0-7, yielding [0-9-[4-7]], or [0-38-9], which matches any character in the string 012389.
The class subtraction is always the last element in the character class. [0-9-[4-7]a-d] is not a valid regular expression. It should be rewritten as [0-9a-d-[4-7]]. The subtraction works on the whole class.
While we can use nested character class subtraction, we cannot subtract two classes sequentially. To subtract ASCII characters and Arabic characters from a class with all Unicode letters, combine the ASCII and Arabic characters into one class, and subtract that, as in [\p{L}-[\p{IsBasicLatin}\p{IsArabic}]].
307 Views
