all Python 3Exceptionsconstruct

else in try-except

handling

The else block runs only if no exception was raised inside try. It separates the happy path from error handling.

Syntax

try:
    ...
except Error:
    ...
else:
    # только при успехе

The point of else isn't tidiness but narrowing the risk zone: lines moved out of try are no longer covered by that except, so a ValueError raised while carrying on can't be silently swallowed by a handler written for parsing. An else clause needs at least one except (else on its own is a syntax error), and the order is try, then else, then finally. Leaving try via return, break or continue skips else entirely.

Examples

try:
    result = int('42')
except ValueError:
    print('error')
else:
    print(f'success: {result}')  # → success: 42

def safe_open(path):
    try:
        f = open(path)
    except FileNotFoundError:
        return None
    else:
        with f:
            return f.read()
print(safe_open('/нет/такого/файла'))  # → None

# else + finally
try:
    x = 10 / 2
except ZeroDivisionError:
    print('zero division')
else:
    print(f'result: {x}')  # → result: 5.0
finally:
    print('done')  # → done

import json
def parse(s):
    try:
        data = json.loads(s)
    except json.JSONDecodeError:
        print('invalid JSON')
    else:
        return data
print(parse('{"a": 1}'))  # → {'a': 1}
print(parse('{'))  # → invalid JSON, затем None

# В else — только код, который НЕ должен ловиться этим except
try:
    n = int('5')
except ValueError:
    print('not a number')
else:
    print(n * 2)  # → 10

See also

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