KeyError — Expert Playground
Raised when a dictionary key is not found
Python Playground
# Exception groups (Python 3.11+)
import sys
print(f"Python {sys.version}")
# Exception hierarchy inspection
print(f"KeyError MRO:")
for cls in KeyError.__mro__:
print(f" {cls.__name__}")
# Exception attributes
try:
d = {}; d["missing"]
except KeyError as e:
print(f"\nException attributes:")
print(f" args: {e.args}")
print(f" __traceback__: {type(e.__traceback__)}")
# Traceback manipulation
import traceback
tb_lines = traceback.format_exception(type(e), e, e.__traceback__)
print(f" Traceback lines: {len(tb_lines)}")
Output
Click "Run" to execute your code
Understanding the exception hierarchy and traceback system helps build robust error handling and debugging tools.
Challenge
Try modifying the code above to explore different behaviors. Can you extend the example to handle a new use case?