How to break my outer loop in Python?

Question

I am working on a project in which I need to execute shell script using Python. And so far everything is looking good.

Below is my Python script which will execute a simple hello world shell script.

MAX_TRIES = 2

jsonStr = '{"script":"#!/bin/bash \\n echoo Hello world 1 "}'
j = json.loads(jsonStr)
shell_script = j['script']

steps = ['step1', 'step2', 'step3']

for step in steps:
    print "start"
    print step
    for i in xrange(MAX_TRIES):
        proc = subprocess.Popen(shell_script, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        (stdout, stderr) = proc.communicate()
        if stderr:
           print "Shell script gave some error..."
           sleep(0.05) # delay for 50 ms
        else:
           print "end" # Shell script ran fine.
           break

In my above script, I am retrying two times if my above shell script gets failed for whatever reason and it is working fine.

Now the question I have is, in my above script, I have a wrong shell script which will get failed. And I have a for loop which will iterate steps list one by one and execute the shell script.

And currently it is getting printed out like this for each steps which is not what I want -

start
step1
Shell script gave some error...
Shell script gave some error...
start
step2
Shell script gave some error...
Shell script gave some error...
start
step3
Shell script gave some error...
Shell script gave some error...

If the shell script failed for the first step, then I don't want to go for step2 but I want to retry two times for each step. Suppose if the shell script execution failed for step1, then I want to retry two times for step1 and if it gets failed twice, then I won't go for step2 but if it passes, then only I will go for step2.

How do I break my outer loops in such a way so that I can accomplish this?

UPDATE:-

for step in steps:
    print "start"
    print step
    for i in xrange(MAX_TRIES):
        proc = subprocess.Popen(shell_script, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        (stdout, stderr) = proc.communicate()
        if stderr:
           print "Shell script gave some error..."
           print stderr
           sleep(0.05) # delay for 50 ms
        else:
            print stdout
            print "end" # Shell script ran fine.
            break
    else:
        break

Veedrac · Accepted Answer · 2013-12-30 03:55:28Z

5

At the end of your script, add

    else:
        break

Loops have an else clause that is called if it exits without a break; so this would be called if the break in the if...else is not called, which is when it failed all three times.

answered Dec 30, 2013 at 3:55

Veedrac

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4 Comments

AKIWEB Over a year ago

Thanks for suggestion but where should I add this? Sorry got confused now.. Can you edit my example with your suggestion.. That will clear my confusion I guess.

Veedrac Over a year ago

Add it at the same indentation as the for loop, at the end.

AKIWEB Over a year ago

I just updated the question.. This is what you meant?

AKIWEB Over a year ago

Yeah it works.. But I am confuse how it works? This is specific to Python world or in general?

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