YAPF - Yet Another Python Formatter

0.43.0 · active · verified Thu Apr 09

YAPF (Yet Another Python Formatter) is an opinionated code formatter for Python, developed by Google. It automatically re-formats Python code to conform to the PEP 8 style guide and other configurable style conventions, aiming to improve code readability and consistency. The current version is 0.43.0, and it generally follows a stable release cadence with updates for Python version support and bug fixes.

Warnings

breaking Python 3.6 support was dropped in YAPF version 0.37.0. Subsequent versions (including 0.43.0) require Python 3.7 or newer.
Fix: Ensure your environment uses Python 3.7 or a later version. Upgrade your Python interpreter if necessary.
gotcha For CLI usage, files are not modified in-place by default. If you run `yapf file.py`, it will print the formatted code to stdout but leave the original file untouched.
Fix: To modify files in-place, always use the `-i` or `--in-place` flag (e.g., `yapf -i file.py`).
gotcha Configuration for programmatic use (e.g., `FormatCode`) does not automatically discover `.style.yapf` or `pyproject.toml` files from the current working directory. You must explicitly pass `style_config` or other parameters.
Fix: Pass `style_config='google'` (or other predefined styles), or a dictionary of style options directly to `FormatCode`. For file-based configuration, load it manually and pass the dictionary, or invoke YAPF via its CLI which handles file discovery.
gotcha Internal AST representation changed from `pytree` to `libcst` in version 0.40.0. While this is primarily an internal refactoring, users who relied on direct interaction with YAPF's internal AST objects might experience compatibility issues.
Fix: Avoid relying on YAPF's internal AST structures. If you need to manipulate ASTs, use `libcst` directly or ensure your integration is compatible with the new underlying library.

Install

pip install yapf Install latest stable version

Imports

FormatCode
```
from yapf.yapf_api import FormatCode
```
FormatCode is the primary function for programmatic formatting. Ensure you import it from the yapf_api submodule.

Quickstart

Demonstrates how to use `FormatCode` to programmatically format a string of Python code, including an example of applying a specific style configuration.

from yapf.yapf_api import FormatCode

unformatted_code = """
def example_function(  arg1,  arg2 = None ):
    if arg1 :
        print(  "Hello", arg1 )
    else:
        return arg2
"""

formatted_code, changed = FormatCode(unformatted_code)

print("--- Original ---")
print(unformatted_code)
print("\n--- Formatted ---")
print(formatted_code)
print(f"\nChanged: {changed}")

# You can also pass style parameters
formatted_code_google, _ = FormatCode(unformatted_code, style_config='google')
print("\n--- Formatted (Google Style) ---")
print(formatted_code_google)

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