yodacheck

AST-based linter that detects and auto-fixes Yoda conditions in Python source files.

A Yoda condition is a comparison where the literal is on the left side:

# Yoda — flagged
if 5 == x: ...
if None == obj: ...
if True == flag: ...

# Normal — not flagged
if x == 5: ...
if obj is None: ...
if flag is True: ...

Features

• Detects all Yoda patterns (==, !=, <, <=, >, >=, is, is not)
• Smart fixes: None == → is None, True/False == → is True/False, all else → swap
• Auto-fix with timestamped .bak backup before writing
• Chained comparisons (1 < x < 3) flagged but not auto-fixed (ambiguous)
• in / not in with literal on left intentionally ignored (normal membership syntax)
• Output formats: pretty (default), plain, json
• Color auto-detected (TTY), forced via --color / --no-color
• Default excludes: .venv, __pycache__, .git, build, dist

Installation

pip install yodacheck

After install the yodacheck command is available globally.

Or install from source:

git clone https://github.com/SytxLabs/yodacheck.git
cd yodacheck
pip install .

Usage

# Scan file or directory
yodacheck path/to/file.py
yodacheck src/

# Multiple paths
yodacheck src/ tests/ setup.py

# Show N context lines per issue
yodacheck src/ --context 1

# Auto-fix (creates .bak backup first)
yodacheck src/ --fix

# Exclude paths (glob or dir name, repeatable)
yodacheck . --exclude "migrations/*" --exclude vendor/

# Output format
yodacheck src/ --format plain
yodacheck src/ --format json

# Color
yodacheck src/ --color
yodacheck src/ --no-color

Output

3 issues · 1 file

  src/auth.py
  42:3   None == token          →  token is None        [is None]
  67:3   0 == status_code       →  status_code == 0
  99:3   1 < retry_count < 5    ⚠ chained, no fix

With --context 1:

  42:3   None == token  →  token is None  [is None]
         40 │ 
         41 │ def validate(token):
         42 │ if None == token:
               ^
         43 │     raise ValueError
         44 │ 

Fix behavior

--fix applies all fixable replacements in one pass per file. Chained comparisons are skipped.

yodacheck src/ --fix
# fixed src/auth.py  (auth.py.bak.20260504T150000Z)

JSON output

yodacheck src/ --format json

[
  {
    "path": "src/auth.py",
    "lineno": 42,
    "col": 3,
    "expr": "None == token",
    "tag": "is None",
    "replacement": "token is None",
    "chained": false
  }
]

tag values: "is None", "is not None", "bool", "" (plain swap), "" with chained: true.

Test file

examples/example.py — runnable collection of every detectable pattern:

yodacheck examples/example.py --color
yodacheck examples/example.py --color --context 1

Running tests

python -m unittest discover -s tests -v

Requirements

Python 3.8+. No external dependencies.