Python Exceptions & Errors

Errors & Exceptions

Python Exceptions & Errors

Errors happen every day. When you know how to interpret, handle, and raise exceptions, you ship faster and debug with confidence.

Practice try/exceptLookup common errors

4

Exception patterns

10

Error pages

5

Traceback tips

Exception Patterns

Master the core mechanisms before tackling individual tracebacks.

• try/except/else/finally
• Raising & chaining
• Custom exception hierarchies
• Reading stack traces

Common Errors

Reference guides for everyday tracebacks pasted into Google.

• ModuleNotFoundError
• ImportError
• NameError
• TypeError
• KeyError & AttributeError
• ZeroDivisionError

Why exceptions matter

• Communicate failure in a structured way.
• Keep your program alive when recoverable conditions occur.
• Provide user-friendly error messages and actionable logs.

Exception hierarchy

• All exceptions inherit from BaseException.
• User-defined exceptions usually derive from Exception.
• Fatal signals (SystemExit, KeyboardInterrupt) also inherit from BaseException—don't swallow them.

Workflow

1. Detect error with try/except.
2. Log detailed context and tracebacks.
3. Raise custom exceptions when you detect business-rule violations.
4. Provide remediation steps in error messages.

Common errors

• Module/path issues (ModuleNotFoundError, ImportError)
• Name resolution (NameError)
• Type mismatches (TypeError, ValueError)
• Container access (IndexError, KeyError, AttributeError)
• Syntax/indentation mistakes
• Math operations (ZeroDivisionError)

Next up in your learning path

Try/except patterns

Wrap risky code with clean error handling.

Practice

Raise better exceptions

Communicate intent with domain-specific errors.

Design

Read tracebacks

Diagnose bugs from stack traces quickly.

Debugging