# pyproject.toml
[tool.ruff]
line-length = 100

[tool.ruff.lint]
select = ["E", "F", "B", "S", "I"]
ignore = ["E501"]  # Line too long (handled by formatter)

[tool.ruff.format]
quote-style = "double"

# Insecure
assert user.is_admin, "Not admin"  # Can be disabled with -O flag

# Secure
if not user.is_admin:
    raise PermissionError("Not admin")

# Violation
password = "admin123"

# Fix
import os
password = os.getenv("PASSWORD")

# Code execution risk
data = pickle.loads(user_input)

# Safe
import json
data = json.loads(user_input)

# Arbitrary code execution
result = eval(user_input)

# Safe
import ast
result = ast.literal_eval(user_input)  # Only literals

# Shared state bug
def add_item(item, items=[]):
    items.append(item)
    return items

# Fix
def add_item(item, items=None):
    if items is None:
        items = []
    items.append(item)
    return items

# Confusing
for i in range(10):
    do_something()  # 'i' not used

# Clear
for _ in range(10):
    do_something()

# error: Argument 1 has incompatible type "str"; expected "int"
def process(x: int) -> int:
    return x * 2

process("5")  # Type error

# Fix
process(int("5"))