How to properly ignore exceptions

Question

When you just want to do a try-except without handling the exception  how do you do it in Python   Is the following the right way to do it   try      shutil rmtree path  except      pass

User · Answer

First I quote the answer of Jack o Connor from this thread  The referenced thread got closed so I write here    There s a new way to do this coming in Python 3 4   from contextlib import suppress  with suppress Exception         your code   Here s the commit that added it  http   hg python org cpython rev 406b47c64480  And here s the author  Raymond Hettinger  talking about this and all sorts of other Python hotness  https   youtu be OSGv2VnC0go t 43m23s  My addition to this is the Python 2 7 equivalent   from contextlib import contextmanager   contextmanager def ignored  exceptions       try          yield     except exceptions          pass   Then you use it like in Python 3 4   with ignored Exception         your code

User · Answer

try        doSomething   except Exception       pass else        stuffDoneIf         TryClauseSucceeds     FYI the else clause can go after all exceptions and will only be run if the code in the try doesn t cause an exception

User · Answer

I usually just do   try      doSomething   except

User · Answer

try      doSomething   except       pass   or  try      doSomething   except Exception       pass   The difference is that the first one will also catch KeyboardInterrupt  SystemExit and stuff like that  which are derived directly from exceptions BaseException  not exceptions Exception   See documentation for details    try statement exceptions

User · Answer

It s generally considered best-practice to only catch the errors you are interested in  In the case of shutil rmtree it s probably OSError    gt  gt  gt  shutil rmtree   fake dir   Traceback  most recent call last             OSError   Errno 2  No such file or directory    fake dir    If you want to silently ignore that error  you would do   try      shutil rmtree path  except OSError      pass   Why  Say you  somehow  accidently pass the function an integer instead of a string  like   shutil rmtree 2    It will give the error  TypeError  coercing to Unicode  need string or buffer  int found  - you probably don t want to ignore that  which can be difficult to debug   If you definitely want to ignore all errors  catch Exception rather than a bare except  statement  Again  why   Not specifying an exception catches every exception  including the SystemExit exception which for example sys exit   uses    gt  gt  gt  try          sys exit 1      except          pass       gt  gt  gt    Compare this to the following  which correctly exits    gt  gt  gt  try          sys exit 1      except Exception          pass      shell       If you want to write ever better behaving code  the OSError exception can represent various errors  but in the example above we only want to ignore Errno 2  so we could be even more specific   import errno  try      shutil rmtree path  except OSError as e      if e errno    errno ENOENT            ignore  No such file or directory   but re-raise other errors         raise

User · Answer

For completeness    gt  gt  gt  def divide x  y           try              result   x   y         except ZeroDivisionError              print  division by zero            else              print  result is   result          finally              print  executing finally clause     Also note that you can capture the exception like this    gt  gt  gt  try          this fails       except ZeroDivisionError as err          print  Handling run-time error    err       and re-raise the exception like this    gt  gt  gt  try          raise NameError  HiThere       except NameError          print  An exception flew by            raise      examples from the python tutorial

User · Answer

When you just want to do a try catch without handling the exception  how do you do it in Python    It depends on what you mean by  handling    If you mean to catch it without taking any action  the code you posted will work   If you mean that you want to take action on an exception without stopping the exception from going up the stack  then you want something like this   try      do something   except      handle exception       raise   re-raise the exact same exception that was thrown

User · Answer

I needed to ignore errors in multiple commands and fuckit did the trick  import fuckit   fuckit def helper        print  before       1 0     print  after1       1 0     print  after2    helper

User · Answer

How to properly ignore Exceptions    There are several ways of doing this    However  the choice of example has a simple solution that does not cover the general case   Specific to the example   Instead of   try      shutil rmtree path  except      pass   Do this   shutil rmtree path  ignore errors True    This is an argument specific to shutil rmtree  You can see the help on it by doing the following  and you ll see it can also allow for functionality on errors as well    gt  gt  gt  import shutil  gt  gt  gt  help shutil rmtree    Since this only covers the narrow case of the example  I ll further demonstrate how to handle this if those keyword arguments didn t exist   General approach  Since the above only covers the narrow case of the example  I ll further demonstrate how to handle this if those keyword arguments didn t exist   New in Python 3 4   You can import the suppress context manager   from contextlib import suppress   But only suppress the most specific exception   with suppress FileNotFoundError       shutil rmtree path    You will silently ignore a FileNotFoundError    gt  gt  gt  with suppress FileNotFoundError           shutil rmtree  bajkjbkdlsjfljsf         gt  gt  gt     From the docs      As with any other mechanism that completely suppresses exceptions    this context manager should be used only to cover very specific errors   where silently continuing with program execution is known to be the   right thing to do    Note that suppress and FileNotFoundError are only available in Python 3   If you want your code to work in Python 2 as well  see the next section   Python 2  amp  3      When you just want to do a try except without handling the exception    how do you do it in Python       Is the following the right way to do it   try       shutil rmtree   path   except       pass    For Python 2 compatible code  pass is the correct way to have a statement that s a no-op  But when you do a bare except   that s the same as doing except BaseException  which includes GeneratorExit  KeyboardInterrupt  and SystemExit  and in general  you don t want to catch those things    In fact  you should be as specific in naming the exception as you can    Here s part of the Python  2  exception hierarchy  and as you can see  if you catch more general Exceptions  you can hide problems you did not expect   BaseException   -- SystemExit   -- KeyboardInterrupt   -- GeneratorExit   -- Exception        -- StopIteration        -- StandardError             -- BufferError             -- ArithmeticError                  -- FloatingPointError                  -- OverflowError                  -- ZeroDivisionError             -- AssertionError             -- AttributeError             -- EnvironmentError                  -- IOError                  -- OSError                       -- WindowsError  Windows                        -- VMSError  VMS              -- EOFError     and so on   You probably want to catch an OSError here  and maybe the exception you don t care about is if there is no directory    We can get that specific error number from the errno library  and reraise if we don t have that   import errno  try      shutil rmtree path  except OSError as error      if error errno    errno ENOENT    no such file or directory         pass     else    we had an OSError we didn t expect  so reraise it         raise    Note  a bare raise raises the original exception  which is probably what you want in this case  Written more concisely  as we don t really need to explicitly pass with code in the exception handling   try      shutil rmtree path  except OSError as error      if error errno    errno ENOENT    no such file or directory         raise

User · Answer

When you just want to do a try catch without handling the exception    how do you do it in Python    This will help you to print what the exception is   i e  try catch without handling the exception and print the exception    import sys try      doSomething   except      print  Unexpected error    sys exc info   0

User · Answer

In Python  we handle exceptions similar to other language  but the difference is some syntax difference  for example   try       Your code in which exception can occur except  lt here we can put in a particular exception name gt         We can call that exception here also  like ZeroDivisionError         now your code   We can put in a finally block also finally        Your code

[python] How to properly ignore exceptions

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