Codegen - Manipulate Code at Scale

Get up and running with Codegen programs in IDEs like VSCode, Cursor and PyCharm.

Make sure to install and initialize Codegen with codegen init

Configuring your IDE Interpreter

Codegen creates a custom Python environment in .codegen/.venv. Configure your IDE to use this environment for the best development experience.

Install the VSCode Python Extensions for LSP and debugging support. We recommend Python, Pylance and Python Debugger for the best experience.

Open the Command Palette (Cmd/Ctrl + Shift + P)
Type “Python: Select Interpreter”

Choose “Enter interpreter path”
Navigate to and select:
```
.codegen/.venv/bin/python
```

Alternatively, create a .vscode/settings.json:

{
  "python.defaultInterpreterPath": "${workspaceFolder}/.codegen/.venv/bin/python",
  "python.analysis.extraPaths": [
    "${workspaceFolder}/.codegen/.venv/lib/python3.12/site-packages"
  ]
}

Open PyCharm Settings/Preferences
Navigate to “Project > Python Interpreter”
Click the gear icon ⚙️ and select “Add”
Choose “Existing Environment”
Set interpreter path to:
```
.codegen/.venv/bin/python
```

Create a New Codemod

Generate the boilerplate for a new code manipulation program using codegen create:

codegen create organize-types \
  -d "Move all TypeScript types to \
      into a centralized types.ts file"

Passing in -d --description will get an LLM expert to compose an initial version for you. This requires a Github account registered on codegen.sh

This will:

Create a new codemod in .codegen/codemods/organize_types/
Generate a custom system-prompt.txt based on your task
Set up the basic structure for your program

The generated codemod includes type hints and docstrings, making it easy to get IDE autocompletion and documentation.

Iterating with Chat Assistants

When you do codegen init, you will receive a system prompt optimized for AI consumption at .codegen/codegen-system-prompt.txt.

If you reference this file in “chat” sessions with Copilot, Cursor, Cody, etc., the assistant will become fluent in Codegen.

Collaborating with Cursor’s assistant and the Codegen system prompt

In addition, when you create a codemod with “-d”, Codegen generates an optimized system prompt in .codegen/codemods/{name}/{name}-system-prompt.txt. This prompt contains:

Relevant Codegen API documentation
Examples of relevant transformations
Context about your specific task

You can also drag and drop the system prompt (available here)file directly into chat windows like ChatGPT or Claude for standalone help.

Running and Testing Codemods

# Run => write changes to disk
codegen run organize-types

# Reset changes on disk
codegen reset

You can also run the program directly via .codegen/.venv/bin/python path/to/codemod.py or via your editor’s debugger

Viewing Changes

We recommend viewing changes in your IDE’s native diff editor.

What’s Next

Explore Tutorials

See real-world examples of codemods in action.

Codegen Guides

Learn about Codegen’s core concepts and features

Introduction

Tutorials

Building with Codegen

Using Codegen in Your IDE

Configuring your IDE Interpreter

Create a New Codemod

Iterating with Chat Assistants

Running and Testing Codemods

Viewing Changes

What’s Next

Explore Tutorials

Codegen Guides

Introduction

Tutorials

Building with Codegen

​Configuring your IDE Interpreter

​Create a New Codemod

​Iterating with Chat Assistants

​Running and Testing Codemods

​Viewing Changes

​What’s Next

Explore Tutorials

Codegen Guides

Configuring your IDE Interpreter

Create a New Codemod

Iterating with Chat Assistants

Running and Testing Codemods

Viewing Changes

What’s Next