Python try / except keep trying until no errors

Question

I have the following code that occasionally crashes due to a permissions bug. I am trying to wrap it up in a try / except statement that will keep trying to launch the driver until successful...

def init_driver():
    ffprofile = webdriver.FirefoxProfile("my_profile")
    ffprofile.add_extension(extension="myaddon.xpi")
    return driver

driver = init_driver()

I have seen examples letting me print a message if an error occurs but how do I get it to keep retrying? Does anybody have an example they can point me at?

Answer 1

Here's a loop that iterates over attempts:

while True:
    try:
        driver = init_driver()
        break
    except Foo:
        continue

Note that this is not a bare except clause. Bare except s are dangerous because they can capture things like NameError that are so rarely meant to be caught. You should put the specific exception you expect to catch here.

Answer 2

Here's one way to do it if you don't want to use a loop. Just recall the function on the exception

 import sys

 def init_driver(tries=0):

     try:
         ffprofile = webdriver.FirefoxProfile("my_profile");
         ffprofile.add_extension(extension="myaddon.xpi")
         return driver

     except Exception: #This should be the exception you expect and not a catch all
         if tries < sys.getrecursionlimit(): #By default 1,000 can be bumped up by setrecursionlimit
             return init_driver(tries+1)
         #just for kicks
         #else:
             #sys.setrecursionlimit(sys.getrecursionlimit() + 1)
             #print("Yes we'll win this game the old-fashioned way, the tried and true way:")
             #print("We'll cheat!")
             #refactor / prettify if's to call init_driver if you want to cheat.
         else:
             print("OH NO RECURSION LIMIT HIT!!!!!! (ノಠ益ಠ)ノ彡┻━┻")

 driver = init_driver()

Answer 3

Other answers are fine but they will keep retrying until it hits the recursion depth limit. Consider adding a retry limit:

def init_driver(retry_limit=10, nretry=0):
    if nretry >= retry_limit:
       return # retry limit reached, maybe raise an exception?
    try:
        ffprofile = webdriver.FirefoxProfile("my_profile");
        ffprofile.add_extension(extension="myaddon.xpi")
    except SomeException:
        return init_driver(nretry=nretry+1)
    return ffprofile

driver = init_driver()

Answer 4

Here is a recursive solution (with keeping track of the retries):

def init_driver(retries=0):
    try:
        ffprofile = webdriver.FirefoxProfile("my_profile");
        ffprofile.add_extension(extension="myaddon.xpi")
    except:
        print('attempt nr. ' + str(retries))
        return init_driver(retries+1)
    return driver

Answer 5

Do like this:

def init_driver():
    driver = None
    ffprofile = webdriver.FirefoxProfile("my_profile");
    ffprofile.add_extension(extension="myaddon.xpi")
    # do something with a valid profile and set driver to something other than None
    return driver

driver = None
while driver is None:
    driver = init_driver()

Answer 6

Just a small change required. Where Foo is the specific exception you get with the permissions bug.

def init_driver():
    try:
        ffprofile = webdriver.FirefoxProfile("my_profile");
        ffprofile.add_extension(extension="myaddon.xpi")
        return driver
    except Foo:
        return init_driver()

driver = init_driver()