[PYTHON] EP 13 Take Advantage of Each Block in try / except / else / finally

• The try/finally cmpound statement lets you run cleanup code regardless of whether exceptions were riased in the try block

• The else block helps you minimize the amount of code in try blocks and visually ditingush the success case from the try/except blocks
• An else block can be used to perform additional actions after successful try block but before common cleanup in finally block

Effective Python

try:
# Excute at the beginning

except Exception as e:
# Execute if an exception is riased in try block.

else:
# Execute if try block does not raise exception.
# Allow user to write code which cause exception here in order to propagate exception to upper stack.

finally:
# Executed at the end anyway.

def load_json_key(data, key):
    try:
      result_dict = json.loads(data) # May raise ValueError
    except ValueError as e:
      raise KeyError from e
    else:
      return result_dict[key] # May raise KeyError