Python Ignore Exception and Go Back to Where I Was

Question

I know using below code to ignore a certain exception, but how to let the code go back to where it got exception and keep executing? Say if the exception \'Exception\' raises in

Answer 1

I posted this recently as an answer to another question. Here you have a function that returns a function that ignores ("traps") specified exceptions when calling any function. Then you invoke the desired function indirectly through the "trap."

def maketrap(*exceptions):
    def trap(func, *args, **kwargs):
        try:
            return func(*args, **kwargs)
        except exceptions:
            return None
    return trap

# create a trap that ignores all exceptions
trapall = maketrap(Exception) 

# create a trap that ignores two exceptions
trapkeyattrerr = maketrap(KeyError, AttributeError)

# Now call some functions, ignoring specific exceptions
trapall(dosomething1, arg1, arg2)
trapkeyattrerr(dosomething2, arg1, arg2, arg3)

In general I'm with those who say that ignoring exceptions is a bad idea, but if you do it, you should be as specific as possible as to which exceptions you think your code can tolerate.

Answer 2

Exceptions are usually raised when a performing task can not be completed in a manner intended by the code due to certain reasons. This is usually raised as exceptions. Exceptions should be handled and not ignored. The whole idea of exception is that the program can not continue in the normal execution flow without abnormal results.

What if you write a code to open a file and read it? What if this file does not exist?

It is much better to raise exception. You can not read a file where none exists. What you can do is handle the exception, let the user know that no such file exists. What advantage would be obtained for continuing to read the file when a file could not be opened at all.

In fact the above answers provided by Aaron works on the principle of handling your exceptions.

Answer 3

you could have all of the do_something's in a list, and iterate through them like this, so it's no so wordy. You can use lambda functions instead if you require arguments for the working functions

work = [lambda: dosomething1(args), dosomething2, lambda: dosomething3(*kw, **kwargs)]

for each in work:
    try:
        each()
    except:
       pass

cleanup()

Answer 4

This is pretty much missing the point of exceptions.

If the first statement has thrown an exception, the system is in an indeterminate state and you have to treat the following statement as unsafe to run.

If you know which statements might fail, and how they might fail, then you can use exception handling to specifically clean up the problems which might occur with a particular block of statements before moving on to the next section.

So, the only real answer is to handle exceptions around each set of statements that you want to treat as atomic

Answer 5

There's no direct way for the code to go back inside the try-except block. If, however, you're looking at trying to execute these different independant actions and keep executing when one fails (without copy/pasting the try/except block), you're going to have to write something like this:

actions = (
    do_something1, do_something2, #...
    )
for action in actions:
    try:
        action()
    except Exception, error:
        pass

Answer 6

Python 3.4 added contextlib.suppress(), a context manager that takes a list of exceptions and suppresses them within the context:

with contextlib.suppress(IOError):
  print('inside')
  print(pathlib.Path('myfile').read_text()) # Boom
  print('inside end')

print('outside')

Note that, just as with regular try/except, an exception within the context causes the rest of the context to be skipped. So, if an exception happens in the line commented with Boom, the output will be:

inside
outside