how do I retry a command only for a specific exception / error

[Steven D'Aprano]

On Fri, 16 Mar 2018 11:04:22 +0530, Ganesh Pal wrote:

> All that I  am trying to do here is write a generic function that will
>  re-retry
> the command  few more times before failing the test


Something like this should do it. It gives up immediately on fatal errors 
and tries again on temporary ones. (You have to specify what you consider 
fatal or temporary, of course.) It uses exponential backup to wait longer 
and longer each time you fail, before eventually giving up. 


delay = 2
for attempts in range(max_attempts):
    try:
        command()
    except PermanentFailureError:
        raise
    except TemporaryFailureError:
        sleep(delay)
        delay *= 2
    else:
        break
else:
    raise RuntimeError("too many attempts")




-- 
Steve