Name: Python Coding Guidelines
Availability: InStock
Author: adarshdigievo

Python Coding Guidelines

Code Style (PEP 8)

4 spaces for indentation (never tabs)
Max line length: 88 chars (Black default) or 79 (strict PEP 8)
Two blank lines before top-level definitions, one within classes
Imports: stdlib → third-party → local, alphabetized within groups
Snake_case for functions/variables, PascalCase for classes, UPPER_CASE for constants

Before Committing

# Syntax check (always)
python -m py_compile *.py
Run tests if present
python -m pytest tests/ -v 2>/dev/null || python -m unittest discover -v 2>/dev/null || echo "No tests found"
Format check (if available)
ruff check . --fix 2>/dev/null || python -m black --check . 2>/dev/null

Python Version

Minimum: Python 3.10+ (3.9 EOL Oct 2025)
Target: Python 3.11-3.13 for new projects
Never use Python 2 syntax or patterns
Use modern features: match statements, walrus operator, type hints

Dependency Management

Check for uv first, fall back to pip:

# Prefer uv if available
if command -v uv &>/dev/null; then
    uv pip install <package>
    uv pip compile requirements.in -o requirements.txt
else
    pip install <package>
fi

For new projects with uv:

uv init

uv venv && source .venv/bin/activate

Pythonic Patterns

# ✅ List/dict comprehensions over loops
squares = [x**2 for x in range(10)]
lookup = {item.id: item for item in items}
✅ Context managers for resources
with open("file.txt") as f:
data = f.read()
✅ Unpacking
first, *rest = items
a, b = b, a  # swap
✅ EAFP over LBYL
try:
value = d[key]
except KeyError:
value = default
✅ f-strings for formatting
msg = f"Hello {name}, you have {count} items"
✅ Type hints
def process(items: list[str]) -> dict[str, int]:
...
✅ dataclasses/attrs for data containers
from dataclasses import dataclass
@dataclass
class User:
name: str
email: str
active: bool = True
✅ pathlib over os.path
from pathlib import Path
config = Path.home() / ".config" / "app.json"
✅ enumerate, zip, itertools
for i, item in enumerate(items):
...
for a, b in zip(list1, list2, strict=True):
...

Anti-patterns to Avoid

# ❌ Mutable default arguments
def bad(items=[]):  # Bug: shared across calls
    ...
def good(items=None):
    items = items or []
❌ Bare except
try:
...
except:  # Catches SystemExit, KeyboardInterrupt
...
except Exception:  # Better
...
❌ Global state
❌ from module import *
❌ String concatenation in loops (use join)
❌ == None (use is None
)
❌ len(x) == 0 (use not x
)

Testing

Use pytest (preferred) or unittest
Name test files
```
test_*.py
```
, test functions
```
test_*
```
Aim for focused unit tests, mock external dependencies
Run before every commit:
```
python -m pytest -v
```

Docstrings

def fetch_user(user_id: int, include_deleted: bool = False) -> User | None:
    """Fetch a user by ID from the database.
Args:
    user_id: The unique user identifier.
    include_deleted: If True, include soft-deleted users.

Returns:
    User object if found, None otherwise.

Raises:
    DatabaseError: If connection fails.
&quot;&quot;&quot;

Quick Checklist

Syntax valid (
```
py_compile
```
)
Tests pass (
```
pytest
```
)
Type hints on public functions
No hardcoded secrets
f-strings, not
```
.format()
```
or
```
%
```
```
pathlib
```
for file paths
Context managers for I/O
No mutable default args

Python Coding Guidelines

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Python Coding Guidelines

Code Style (PEP 8)

Before Committing

Run tests if present

Format check (if available)

Python Version

Dependency Management

Pythonic Patterns

✅ Context managers for resources

✅ Unpacking

✅ EAFP over LBYL

✅ f-strings for formatting

✅ Type hints

✅ dataclasses/attrs for data containers

✅ pathlib over os.path

✅ enumerate, zip, itertools

Anti-patterns to Avoid

❌ Bare except

❌ Global state

❌ from module import *

❌ String concatenation in loops (use join)

❌ == None (use is None)

❌ len(x) == 0 (use not x)

Testing

Docstrings

Quick Checklist

Quick Start

Manual Installation

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❌ == None (use
`is None`
)

❌ len(x) == 0 (use
`not x`
)