Repren

Repren - Multi-Pattern Search and Replace

Full documentation: Run uvx repren@latest --docs for all options, flags, and advanced usage.

Multi-pattern search/replace tool for bulk refactoring with simultaneous replacements, file/directory renaming, and case-preserving transformations.

Quick Start

Always start with dry-run to preview changes:

uvx repren@latest --from='old_name' --to='new_name' --full --dry-run src/

Then execute if output looks correct:

uvx repren@latest --from='old_name' --to='new_name' --full src/

When to Use Repren

Use repren for:

• Large-scale code refactoring (renaming across many files)
• Simultaneous multi-pattern replacements
• File and directory renaming based on content patterns
• Case-preserving identifier transformations
• Operations requiring dry-run validation and backups
• Swapping or circular renames (foo↔bar)

Don’t use repren for:

• Single-file small edits or replacements (use Edit tool instead)
• Language-aware semantic refactoring (use AST tools like ast-grep, ts-morph)
• Operations requiring precise line-by-line control (use Edit tool)

Core Features

Simultaneous Multi-Pattern Replacement

Create a patterns file with tab-separated pairs:

old_function	new_function
OldClass	NewClass
CONSTANT_OLD	CONSTANT_NEW

Apply all patterns at once:

uvx repren@latest --patterns=patterns.txt --full src/

Repren handles overlapping patterns intelligently: you can swap names (foo↔bar) in a single pass.

Case-Preserving Transformations

Handle all case variants automatically:

uvx repren@latest --from='my_var' --to='my_function' --preserve-case --full src/

Transforms: my_var→my_function, myVar→myFunction, MyVar→MyFunction, MY_VAR→MY_FUNCTION.

File and Directory Renaming

With --full, in addition to searching and replacing content, repren will rename files and directories matching the patterns.

uvx repren@latest --from='old_module' --to='new_module' --full src/

Renames files and directories, creating parent directories as needed. Files never clobber: numeric suffixes are added if conflicts arise.

Regex Patterns with Capture Groups

Use full Python regex syntax with backreferences:

uvx repren@latest --from='figure ([0-9]+)' --to='Figure \1' --full docs/

Pattern file example:

def (\w+)\(self\)	def \1(self, context)
class Old(\w+)	class New\1

Safety and Backup Management

Atomic Operations with Backups

All modifications create .orig backup files automatically. Original files never truncated on errors.

Dry Run

Always preview changes first:

uvx repren@latest --dry-run --patterns=patterns.txt --full mydir/

Shows exactly what would change without modifying files.

Undo Changes

Restore from backups if needed:

uvx repren@latest --undo --from='old' --to='new' --full src/

Clean Backups

Remove backups when satisfied:

uvx repren@latest --clean-backups src/

Common Workflows

Large Codebase Refactoring

1. Preview changes:

uvx repren@latest --from='OldName' --to='NewName' --preserve-case --word-breaks --full --dry-run src/

2. Execute if output looks correct:

uvx repren@latest --from='OldName' --to='NewName' --preserve-case --word-breaks --full src/

3. Review changes, test, then clean backups:

uvx repren@latest --clean-backups src/

Filtering Files

Include only specific file types:

uvx repren@latest --patterns=patterns.txt --include='.*\.(py|pyi)$' --full src/

Exclude directories:

uvx repren@latest --patterns=patterns.txt --exclude='tests|node_modules|__pycache__' --full src/

Word Boundaries

Match only at word boundaries (safer for variable names):

uvx repren@latest --from='var' --to='variable' --word-breaks --full src/

Literal Patterns

Treat patterns as literal strings (not regex):

uvx repren@latest --from='file.txt' --to='data.txt' --literal --full docs/

Multi-Line Patterns

Process entire files at once for patterns spanning lines:

uvx repren@latest --patterns=patterns.txt --at-once --full src/

Machine-Readable Output

Use JSON format for programmatic processing:

uvx repren@latest --format=json --from='old' --to='new' --full src/

Returns structured data about all changes made.

Key Flags

Most important flags (run uvx repren@latest --docs for complete list):

Pattern File Format

Tab-separated pattern/replacement pairs:

pattern<TAB>replacement
another<TAB>replacement
# Comments start with #

Supports regex with capture groups (\w+) and backreferences \1, \2. First match wins for overlaps.

Notes

• All pattern matching uses Python regex syntax
• Replacements are line-by-line by default, use --at-once for full-file
• Multiple patterns matched first, then all replaced (enables swaps)
• Binary files supported (patterns specified as strings, data handled as bytes)
• File permissions preserved
• Operations are atomic - temp files used, then renamed
• Default excludes hidden files (starting with .), customizable with --exclude
• Backup files (.orig by default) always ignored in recursive operations

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