pycastic 0.0.3

Python refactoring CLI tool powered by LibCST

pycastic

Python refactoring CLI tool powered by LibCST.

Installation

pip install pycastic

Usage

pycastic uses a unified command interface that automatically detects the operation based on source and target arguments:

pycastic SOURCE TARGET [OPTIONS]

The project root is auto-detected by looking for pyproject.toml or .git directory, or can be specified with --root.

Operations

Symbol Operations (source contains ::)

Example	Description
pycastic src/utils.py::old_func src/utils.py::new_func	Rename symbol
pycastic src/utils.py::helper dest.py	Move symbol
pycastic src/utils.py::helper dest.py::new_name	Move + rename
pycastic src/utils.py::a,b,c dest.py	Move multiple symbols

File Operations (source is a file path)

Example	Description
pycastic src/old.py src/new.py	Rename file
pycastic src/utils.py lib/utils.py	Move file
pycastic src/utils.py lib/	Move file to directory

Target Formats

Format	Example	Description
file.py::Symbol	utils.py::helper	Symbol by name
file.py::A,B,C	utils.py::foo,bar	Multiple symbols
file.py:line:col	utils.py:10:5	Symbol at position

Options

Option	Effect
--dry-run / -n	Preview changes without applying
--root PATH / -r	Specify project root (auto-detected by default)
--include-deps	Auto-include shared dependencies in the move
--shared-file	Extract shared deps to default file ({source}_common.py)
--shared-file-path PATH	Extract shared deps to specified file

Move Behavior Rules

Scenario	Behavior
Symbol uses external imports	Imports copied to destination
Symbol uses internal dep (unused elsewhere)	Dep moved automatically
Symbol uses internal dep (used elsewhere)	Error: use --include-deps or --shared-file
Other files import moved symbol	Imports updated to new location
Original file uses moved symbol	Import added from new location
Original file has unused imports after move	Unused imports removed

Examples

Rename a symbol

# Rename by name
pycastic src/utils.py::old_function src/utils.py::new_function

# Rename by position (line:column)
pycastic src/module.py:10:5 src/module.py::new_name

Move symbols

# Move a function (auto-includes unused internal dependencies)
pycastic src/utils.py::process_data src/processors.py

# Move multiple related functions together
pycastic src/utils.py::parse,validate,transform src/parsers.py

# Preview what would happen
pycastic src/utils.py::my_func dest.py --dry-run

Handling shared dependencies

When moving a symbol that depends on another symbol in the same file, pycastic checks if that dependency is used by other remaining code:

# If shared dependency detected, you have two options:

# Option 1: Include shared deps in the move
pycastic src/utils.py::func_a dest.py --include-deps

# Option 2: Extract shared deps to a common file (default: utils_common.py)
pycastic src/utils.py::func_a dest.py --shared-file

# Option 3: Extract shared deps to a specific file
pycastic src/utils.py::func_a dest.py --shared-file-path src/common.py

Rename and move files

# Rename a file (updates all imports)
pycastic src/old_name.py src/new_name.py

# Move a file to a new directory (updates all imports)
pycastic src/utils.py lib/

How It Works

pycastic uses LibCST to parse and transform Python code while preserving formatting. When moving symbols:

1. Dependency Analysis: Analyzes what imports and internal symbols the target depends on
2. Smart Resolution: Determines which dependencies should move automatically vs. require user input
3. Import Management: Updates imports in all affected files
4. Cleanup: Removes unused imports from the original file

License

MIT