CODEWITHSUNDEEP
pythonexception
Sanmesh Udhayakumar
Sanmesh Udhayakumar

Reputation: 3

In Python on exceptions, how do I redo line that caused the exception

For my application, I am using python interface to read registers of a microcontroller. Sometimes, the read fails and causes an Exception. Ideally what I'd like to do is on an exception, I would like to go back to the same line that had an exception and redo it. This means, essentially go back to the statement that failed at reading a register. I can for a single read do the following:

while ReadSuccess == 0:
  try:
    readregister();
    faultReadSuccess = 1
  except (KeyboardInterrupt, SystemExit):
    print "Program manually stopped through Ctrl-C"
    raise
  except:
    faultReadSuccess = 0
    print "Reading failure"
    time.sleep(.5)

This essentially on a single read just repeats the read till it passes. However, I have several register read commands scattered through my program and these are flow-sensitive reads, and I can't just start at the beginning of the code or a section of code with the reads through a while loop or something. Rather, if a read fails, I need to directly redo that read again till it passes and then continue on.

However, I do no know how to do this without for each individual read, do the code mentioned above. I tried looking for a "jump to"/"go to" the previous line equivalent, but I cannot find anything. Is there something that would allow me to on exception just repeat the line that failed?

Upvotes: 0

Views: 815

Answers (2)

Quinn
Quinn

Reputation: 4504

I suggest you create a new function to retry the read_register(), and pass a parameter to control how many times you'd like to retry. For example, to define a function like:

def read_retry(read_reg, n):
"""
"read_reg" is one of your read_register functions;
"n" is the retry times.
"""
    i = 0    # i is the counter
    while i < n:
        try:
            read_reg()
            break    # if success, then exit the loop
        except:            
            print "Reading failure for {} time(s)".format(i+1)
            time.sleep(0.5)
            i = i + 1

Say, you want to retry read_register_1() for 3 times. Just call read_retry(read_register_1, 3).

Upvotes: 2

Chris Curvey
Chris Curvey

Reputation: 10389

so you'll have to do something like this:

while True:
   try:
     read_register_1()
   except:
     time.sleep(0.5)
   else:
     break

while True:
   try:
     read_register_2()
   except:
     time.sleep(0.5)
   else:
     break

Upvotes: 0

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