how to make the below code look better

Wed Dec 2 08:28:08 EST 2015

On Wed, 2 Dec 2015 11:11 pm, Ganesh Pal wrote:
> Hello team,
>> I need suggestion to improve the below code , Iam on Linux and python 2.7
>> if not os.path.ismount("/tmp"):
> sys.exit("/tmp not mounted.")

This is good enough for quick and dirty scripts, but this is vulnerable to a
race condition. It may be that /tmp is mounted *now*, but a millisecond
later (before you can use it) another process unmounts it.
This is called a "time of check to time of use" bug:
https://cwe.mitre.org/data/definitions/367.html
https://www.owasp.org/index.php/Time_of_check,_time_of_use_race_condition
https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use
and can be a serious software vulnerability.
If this code is only being used under trusted conditions, then it is
probably okay, otherwise you should reconsider your strategy.
(Besides, how often do you unmount /tmp?)
> else:
> if create_dataset() and check_permission():

this with:
elif create_dataset() and check_permission():
but again be mindful of the risk of race conditions.
> try:
> run_full_back_up()
> run_partial_back_up()
> except Exception, e:
> logging.error(e)
> sys.exit("Running backup failed")
> if not validation_errors():
> sys.exit("Validation failed")

I would swap the sense of validation_errors(). Currently, it looks like it
returns True if there are *no* errors, and False if there are errors. That
seems confusing and easy to get wrong. 
 if validation_errors():
 sys.exit("Validation failed")
reads better and is easier to understand. Now validation_errors() returns
true if there are errors, and false if there are no errors.
> else:
> try:
> compare_results()
> except Exception, e:
> logging.error(e)
> sys.exit("Comparing result failed")
>> Question 1:
>> 1. if create_dataset() and check_permission():
> Iam assuming that if statement will be executed only if both the
> functions are true ?

Correct.
> 2. Can I have a if statement within if else ? , some how I feel its messy

Yes you can, but elif is usually nicer, and saves a level of indentation.
-- 
Steven