Exception Chaining & Best Practices

# Exception chaining (raise from)
class DatabaseError(Exception): pass

def query_database():
    try:
        result = {}["missing_key"]
    except KeyError as e:
        raise DatabaseError("Query failed") from e

try:
    query_database()
except DatabaseError as e:
    print(f"DB Error: {e}")
    print(f"Caused by: {e.__cause__}")

# Best practices
# 1. Be specific — catch specific exceptions
# BAD:
# try: ... except: pass

# GOOD:
try:
    value = int("hello")
except ValueError as e:
    print(f"Conversion error: {e}")

# 2. Don't suppress errors silently
# BAD: except: pass
# GOOD: except ValueError: logger.warning("...")

# 3. Use EAFP (Easier to Ask Forgiveness)
data = {"name": "Alice"}

# EAFP (Pythonic)
try:
    value = data["age"]
except KeyError:
    value = "Unknown"

# vs LBYL (Look Before You Leap)
value = data["age"] if "age" in data else "Unknown"

print(f"Age: {value}")