How could I go about doing something like this
I believe I would have to make use of try but I haven't quite come around yet to how to use it in this particular example.
It doesn't sound like you want to do a nested try-catch at all. Exceptions as control flow are a gnarly anti-pattern, and where you can avoid it, you should.
In this scenario, avoidance is easy. In the method that you describe, you want to be sure that a file exists before you do some operations on it. You also have a method to "correct" the path should it not. If both attempts fail, then you want to bail out.
With that into account, we would want to use os.path.isfile for this.
from os.path import isfile
def something(filepath):
# Don't mutate the parameter if you can help it.
p = filepath
if not isfile(p):
p = correct_path(p)
if not isfile(p):
raise Error("Cannot find file {} after correction to {}, aborting.".format(filepath, p))
with open(p, 'r') as f:
# Rest of file operations here
This works for an arbitrary number of tries; I set it to two since that's what you want.
tries = 2
while True:
try:
step1()
except CatchThisException:
tries -= 1
if tries: # if tries != 0
step3()
continue # not necessary, just for clarity
else:
raise # step 4
else:
break # step 2
Try a nested try catch:
try:
do_something() #if this works, will skip rest and continue
except:
do_fix_function() #on error, do extra function
try:
do_something() #try again
except:
throw error() #if it fails this time, stop and throw an error
Note that if your do_fix_function() can also fail, you might want to put it inside the second try statement instead
You can use retrying package to solve your retry attempt. Just write a block of code that keeps repeating on failure, until max retries is hit
For example:
import random from retrying import retry
@retry
def do_something_unreliable():
if random.randint(0, 10) > 1:
raise IOError("Broken sauce, everything is hosed!!!111one")
else:
return "Awesome sauce!"
print do_something_unreliable()
@retry does not allow for a “fix” function to be run between retries (unless you do hacky side effects). The OP also only wants to retry once (which is possible, but not done in this answer). @retry is for flaky functions, not deterministic failures. I suggest that next time you read the question more carefully before rushing to judgement and an answer.
tryas a means of program flow.something()is a file-altering operation that, if the file doesn't exist, will blow up. The later mentionedafunction()is a file-searching function to correct the file's name sosomething()will run correctly.