python catch exception and continue try block

Question

Can I return to executing try-block after exception occurs? (The goal is to write less) For Example:

try:
    do_smth1()
except:
    pass

try:
    do_smth2()
except:
    pass

vs

try:
    do_smth1()
    do_smth2()
except:
    ??? # magic word to proceed to do_smth2() if there was exception in do_smth1

Answer 1

No, you cannot do that. That's just the way Python has its syntax. Once you exit a try-block because of an exception, there is no way back in.

What about a for-loop though?

funcs = do_smth1, do_smth2

for func in funcs:
    try:
        func()
    except Exception:
        pass  # or you could use 'continue'

Note however that it is considered a bad practice to have a bare except. You should catch for a specific exception instead. I captured for Exception because that's as good as I can do without knowing what exceptions the methods might throw.

Answer 2

I don't think you want to do this. The correct way to use a try statement in general is as precisely as possible. I think it would be better to do:

try:
    do_smth1()
except Stmnh1Exception:
    # handle Stmnh1Exception

try:
    do_smth2()
except Stmnh2Exception:
    # handle Stmnh2Exception

Answer 3

You could iterate through your methods...

for m in [do_smth1, do_smth2]:
    try:
        m()
    except:
        pass

Answer 4

special_func to avoid try-except repetition:

def special_func(test_case_dict):
    final_dict = {}
    exception_dict = {}

    def try_except_avoider(test_case_dict):

        try:
            for k,v in test_case_dict.items():
                final_dict[k]=eval(v) #If no exception evaluate the function and add it to final_dict

        except Exception as e:
            exception_dict[k]=e #extract exception
            test_case_dict.pop(k)
            try_except_avoider(test_case_dict) #recursive function to handle remaining functions

        finally:  #cleanup
            final_dict.update(exception_dict)
            return final_dict #combine exception dict and  final dict

    return try_except_avoider(test_case_dict) 

Run code:

def add(a,b):
    return (a+b)
def sub(a,b):
    return (a-b)
def mul(a,b):
    return (a*b)

case = {"AddFunc":"add(8,8)","SubFunc":"sub(p,5)","MulFunc":"mul(9,6)"}
solution = special_func(case)

Output looks like:

{'AddFunc': 16, 'MulFunc': 54, 'SubFunc': NameError("name 'p' is not defined")}

To convert to variables:

locals().update(solution)

Variables would look like:

AddFunc = 16, MulFunc = 54, SubFunc = NameError("name 'p' is not defined")

Answer 5

one way you could handle this is with a generator. Instead of calling the function, yield it; then whatever is consuming the generator can send the result of calling it back into the generator, or a sentinel if the generator failed: The trampoline that accomplishes the above might look like so:

def consume_exceptions(gen):
    action = next(gen)
    while True:
        try:
            result = action()
        except Exception:
            # if the action fails, send a sentinel
            result = None

        try:
            action = gen.send(result)
        except StopIteration:
            # if the generator is all used up, result is the return value.
            return result

a generator that would be compatible with this would look like this:

def do_smth1():
    1 / 0

def do_smth2():
    print "YAY"

def do_many_things():
    a = yield do_smth1
    b = yield do_smth2
    yield "Done"

>>> consume_exceptions(do_many_things())
YAY

Note that do_many_things() does not call do_smth*, it just yields them, and consume_exceptions calls them on its behalf

Answer 6

'continue' is allowed within an 'except' or 'finally' only if the try block is in a loop. 'continue' will cause the next iteration of the loop to start.

So you can try put your two or more functions in a list and use loop to call your function.

Like this:

funcs = [f,g]
for func in funcs:
    try: func()
    except: continue

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