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I can't figure out how to handle exception for python 'with' statement. If I have a code: with open("a.txt") as f: print f.readlines() I really want to handle 'file not found exception' in order to do something. But I can't write. with open("a.txt") as f: print f.readlines() except: print 'oops' and can't write
Never use exceptions for flow-control. Exceptions exist for exceptional situations: events that are not a part of normal execution. Consider 'find' on a string returning -1 if the pattern isn't found, but indexing beyond the end of a string raises an exception. Not finding the string is normal execution. Handle exceptions at the level that ...
Note that a Queue.Queue (as suggested in other answers) is not necessary in this simple case where the thread throws at most 1 exception and completes right after throwing an exception. We avoid race conditions by simply waiting for the thread to complete. For example, extend ExcThread (below), overriding excRun (instead of run). Python 2.x:
Raise exception (args) from original_exception. This statement is used to create exception chaining in which an exception that is raised in response to another exception can contain the details of the original exception - as shown in the example below. class MyCustomException(Exception): pass. a = 10.
Nov 16, 2011 · Conditionally handle errors using a conditional statement in the except block: def my_func(my_arg, handle_exceptions): try: do_something(my_arg) except Exception: if handle_exceptions: print("my_func is handling the exception") raise. Re-raising the exception by using the bare raise statement within the except block will not put another stack ...
Jan 4, 2011 · This example uses the new "as" syntax to catch the exception, supported in Python 2.6 and later. The output of the above is: DEBUG:root:This message should go to the log file. ERROR:root:integer division or modulo by zero. Traceback (most recent call last): File "untitled-1.py", line 6, in <module>. 1/0. ZeroDivisionError: integer division or ...
Aug 17, 2009 · then now it boils down to a question of principle. your first code is basically the same as mine, except that you simply dont nest the exceptions, as I did in an "else"-tree, which was suggested in the python docs. which one is better practise? the docs state that else should always be preferred rather than additional statements in the try block. its basically the same question with if's: is it better to return before another if, or is it better to nest the ifs conditionally.
ok_codes_int = isinstance(ok_status_codes, int) ok_codes_list = isinstance(ok_status_codes, list) if ok_status_codes != None and (not ok_codes_int) and (not ok_codes_list): raise Exception(f'ok_status_codes must be None, list or int, ' +\ f'not {type(ok_status_codes)} ({ok_status_codes})') success, deliverable = requests_call(method, url, **kwargs) if not success: deliverable.failure_reason = 'requests_call returned False: deliverable is Exception' deliverable.failure_code = 1 return (False ...
The suppress context manager. The accepted answer is really 4 lines of code, minimum: try: do_something() except (IDontLikeYouException, YouAreBeingMeanException) as e: pass. The try, except, pass lines can be handled in a single line with the suppress context manager, available in Python 3.4: from contextlib import suppress.
Handling the exception is the way to go: try: gotdata = dlist[1] except IndexError: gotdata = 'null'. Of course you could also check the len() of dlist; but handling the exception is more intuitive. edited Oct 27, 2017 at 12:25. answered Aug 10, 2012 at 13:17. ThiefMaster.
