Regex Search and Replace Tips in Notepad++

# 1. Introduction to Regular Expressions

Regular expressions are a powerful tool for matching string patterns, defined by a sequence of characters that describe a search pattern. In text processing, regular expressions can be used for searching, replacing, and matching strings that fit specific criteria.

In Notepad++, regular expressions are extensively used in search and replace operations, providing users with robust text manipulation capabilities.

### 1.1 What are Regular Expressions

Regular expressions consist of a combination of literal characters (like letters and numbers) and metacharacters (like ., *, ?), forming an expression that describes a pattern of characters. It allows for efficient text searching and matching.

### 1.2 Application of Regular Expressions in Text Editors

In text editors, regular expressions aid users in quickly locating and processing text content that adheres to specific rules, thus enhancing editing efficiency.

### 1.3 Supported Regular Expression Syntax in Notepad++

Notepad++ supports basic regular expression syntax, such as `.` (matches any character) and `*` (matches zero or more times). Additionally, it supports advanced regular expression syntax, such as `^` (matches the start of a line) and `$` (matches the end of a line), enabling users to perform searches and replacements with greater precision.

# 2. Regular Expression Search in Notepad++

Regular expression search is about finding content in text that fits a specific pattern, aiding users in quickly locating and filtering information. In Notepad++, regular expressions can also be used for searching. The following will introduce how to perform regular expression search and some useful techniques.

### 2.1 How to Open the Search Box

To perform regular expression search in Notepad++, you first need to open the search box. You can open it with the shortcut Ctrl + F, then check the "Regular expression" option in the search box to start using regular expressions for your search.

### 2.2 Basic Regular Expression Search Techniques

1. **Matching a Single Character**: Use `.` to match any single character.
- **Example Code**:

      # Find all words containing "cat"
      search_pattern = r'\b\w*cat\w*\b'

- **Code Comment**: This regular expression matches all words containing "cat", `\b` denotes a word boundary, and `\w*` denotes a match of 0 or more word characters.

2. **Matching a Specific Set of Characters**: Use `[...]` to match any single character within the brackets.
- **Example Code**:

      # Find all words containing a vowel
      search_pattern = r'\b\w*[aeiou]\w*\b'

- **Code Comment**: This regular expression matches all words containing a vowel, `[aeiou]` matches any vowel character.

### 2.3 Advanced Regular Expression Search Techniques

1. **Using Capturing Groups**: Use `()` to create a capturing group, which can be referenced in replacements.
- **Example Code**:

      # Replace date format to YYYY-MM-DD
      search_pattern = r'(\d{4})/(\d{2})/(\d{2})'
      replace_pattern = r'\1-\2-\3'

- **Code Comment**: This regular expression matches the date format and uses capturing groups to replace it in the YYYY-MM-DD format.

2. **Using Quantifiers**: Use `*` to match the preceding character 0 or more times, `+` to match it 1 or more times, and `?` to match it 0 or 1 time.
- **Example Code**:

      # Match repeated consecutive words
      search_pattern = r'\b(\w+)\s\1\b'

- **Code Comment**: This regular expression matches repeated consecutive words, `\1` references the content captured by the preceding group, ensuring consecutive duplicates are matched.

With these basic and advanced regular expression search techniques, regular expression search in Notepad++ becomes more efficient and convenient, enabling more accurate location and filtering of the desired information.

# 3. Regular Expression Replacement in Notepad++

Performing regular expression replacement in Notepad++ is straightforward and efficient, aiding in rapid batch modification of text content. Below will introduce how to conduct regular expression replacement in Notepad++, including how to open the replace box and basic and advanced replacement techniques.

#### 3.1 How to Open the Replace Box

To perform regular expression replacement in Notepad++, you first need to open the replace box. You can open it with the shortcut Ctrl + H or by selecting "Search" -> "Replace" from the menu bar.

#### 3.2 Basic Regular Expression Replaceme