retrrry 2.0.0

Retry for Python3. No dependency.

Retrrry

Decorate flaky functions with @retry to apply retrying logic.

Simplest way to use retrrry is actually to copy the code in retry.py and use it in your project, since there is no dependencies other than the standard library.

@retry
def unreliable_func():
    import random
    if random.randint(0, 10) < 5:
        raise IOError('Fail')
    else:
        return 'Success'

Configurations

• Specify stop condition (i.e. limit by number of attempts)
• Specify wait condition (i.e. exponential backoff sleeping between attempts)
• Specify certain Exceptions
• Specify expected returned result

Installation

pip install retrrry

from retrrry import retry

Examples

The default behavior is to retry forever without waiting:

@retry
def never_stop_never_wait():
    print('Retry forever, ignore Exceptions, no wait between retries')

Set the number of attempts before giving up:

@retry(stop_max_attempt_number=7)
def stop_after_7_attempts():
    print('Stopping after 7 attempts')

Set a boundary for time for retry:

@retry(stop_max_delay=10000)
def stop_after_10_s():
    print('Stopping after 10 seconds')

Set wait time between retries:

@retry(wait_fixed=2000)
def wait_2_seconds():
    print('Wait 2 second between retries')

Inject some randomness:

@retry(wait_random_min=1000, wait_random_max=2000)
def wait_1_to_2_seconds():
    print('Randomly wait 1 to 2 seconds between retries')

Use exponential backoff:

@retry(wait_exponential_multiplier=1000, wait_exponential_max=10000)
def wait_exponential_1000():
    print(
        'Wait 2^i * 1000 milliseconds after ith retry, up to 10 seconds, then 10 seconds afterwards'
    )

Deal with specific exceptions:

def retry_if_io_error(exception):
    return isinstance(exception, IOError)

@retry(retry_on_exception=retry_if_io_error)
def might_have_io_error():
    print('Retry if an IOError occurs, raise any other errors')

@retry(retry_on_exception=retry_if_io_error, wrap_exception=True)
def might_have_io_error_raise_retry_error():
    print('Retry if an IOError occurs, raise any other errors wrapped in RetryError')

Alter the behavior of retry based on a function return value:

def retry_if_result_none(result):
    return result is None

@retry(retry_on_result=retry_if_result_none)
def might_return_none():
    print('Retry if return value is None')

# Or retry if result is equal to 1
@retry(retry_on_result=lambda res: res == 1)
def might_return_none():
    print('Retry if return value is 1')

Finally, we can always combine all of the configurations.