Python tenacity: How to retry if exception is NOT of a certain type?

Question

How to retry a function if the exception is NOT of a certain type using Python's tenacity?

retry_if_exception_type will retry if there is risen an exception of a certain type. not does not seems to work placed before the method nor before its arguments.

retry_unless_exception_type, on the other side, loops forever, even if there is not risen error, until there is risen error of a certain type.

score 3 · Accepted Answer · answered Apr 19 '22 at 04:15

retry_if_not_exception_type is available since version 8.0.0

Retries except an exception has been raised of one or more types.

So if you use retry_if_not_exception_type((ValueError, OSError)), it will retry for any exception, except ValueError or OSError.

score 1 · Answer 2 · answered Mar 11 '20 at 12:33

I had to create my own class for that:

class retry_if_exception_unless_type(retry_unless_exception_type):
    """Retries until successful outcome or until an exception is raised of one or more types."""

    def __call__(self, retry_state):
        # don't retry if no exception was raised
        if not retry_state.outcome.failed:
            return False
        return self.predicate(retry_state.outcome.exception())

score 0 · Answer 3 · answered Jan 29 '20 at 19:20

0

using retry_unless_exception_type() combined with stop_after_attempt() worked for me to accomplish this. the stop_after_attempt() prevents the infinite looping.

answered Jan 29 '20 at 19:20

Ben Sachs

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@retry(wait=wait_random_exponential(multiplier=3, max=30), stop=stop_after_attempt(5), reraise=True, retry=retry_unless_exception_type(NotFoundException)) – Ben Sachs Jan 29 '20 at 19:22

mikenerone · Answer 4 · 2021-04-22T19:30:32.990

0

Breaking it down a bit, what you want is to retry if:

an exception is raised
(and) unless the exception is of a certain type

So write that:

retry_if_exception_type() & retry_unless_exception_type(ErrorClassToNotRetryOn)

edited Apr 22 '21 at 19:30

answered Apr 22 '21 at 19:18

mikenerone

1,937
3
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Python tenacity: How to retry if exception is NOT of a certain type?

4 Answers4