Exception Chaining & Best Practices
Exception chaining preserves the original error context. Follow best practices: be specific, don't suppress errors silently, and use logging.
10 min•By Priygop Team•Updated 2026
Exception Best Practices
Exception 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}")Tip
Tip
Use 'raise from e' to chain exceptions and preserve the original traceback. It helps debugging immensely.
Diagram
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Catch specific exceptions. Use else for success logic. finally for cleanup. Custom exceptions for your domain.
Common Mistake
Warning
Swallowing exceptions silently with except: pass. At minimum, log the error. Silent failures are the hardest bugs to find.
Practice Task
Note
(1) Chain exceptions with 'raise from'. (2) Create a retry decorator for transient errors. (3) Log exceptions properly.