Cheat sheet · Class 12 · CBSE · Science Computer Science
Exception Handling in Python cheat sheet
The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.
CBSE Class 12 · Computer Science
Cheat sheet
Chapter 3Exception Handling in Python
try → except → else → finally.
1. Errors
- Syntax errors: caught before running.
- Exceptions: errors during execution.
2. Built-in Exceptions
| Exception | When |
|---|---|
| ZeroDivisionError | division by zero |
| ValueError | right type, wrong value (int('abc')) |
| TypeError | wrong type for an operation |
| NameError | undefined variable |
| IndexError | index out of range |
| KeyError | missing dictionary key |
| IOError / FileNotFoundError | file problems |
| EOFError | input() hits end of file |
3. Handling
try:
x = int(input())
print(10 / x)
except ZeroDivisionError:
print('Zero!')
except ValueError:
print('Not a number')
else:
print('OK')
finally:
print('Done')
4. Raising
- raise ValueError('message') throws an exception.
- assert condition, 'message' checks a condition.
5. Key Points
- else runs only if no exception.
- finally always runs.
- A bare except catches everything.
- Exceptions propagate up the call stack.
Remember: try/except/else/finally | common exceptions | raise & assert
Exception Handling in Python: questions and notes
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