How to print an exception in Python

Question

try      something here except      print  the whatever error occurred      How can I print the error exception in my except  block

User · Answer

One has pretty much control on which information from the traceback to be displayed/logged when catching exceptions.

The code

with open("not_existing_file.txt", 'r') as text:
    pass

would produce the following traceback:

Traceback (most recent call last):
  File "exception_checks.py", line 19, in <module>
    with open("not_existing_file.txt", 'r') as text:
FileNotFoundError: [Errno 2] No such file or directory: 'not_existing_file.txt'

Print/Log the full traceback

As others already mentioned, you can catch the whole traceback by using the traceback module:

import traceback
try:
    with open("not_existing_file.txt", 'r') as text:
        pass
except Exception as exception:
    traceback.print_exc()

This will produce the following output:

Traceback (most recent call last):
  File "exception_checks.py", line 19, in <module>
    with open("not_existing_file.txt", 'r') as text:
FileNotFoundError: [Errno 2] No such file or directory: 'not_existing_file.txt'

You can achieve the same by using logging:

try:
    with open("not_existing_file.txt", 'r') as text:
        pass
except Exception as exception:
    logger.error(exception, exc_info=True)

Output:

__main__: 2020-05-27 12:10:47-ERROR- [Errno 2] No such file or directory: 'not_existing_file.txt'
Traceback (most recent call last):
  File "exception_checks.py", line 27, in <module>
    with open("not_existing_file.txt", 'r') as text:
FileNotFoundError: [Errno 2] No such file or directory: 'not_existing_file.txt'

Print/log error name/message only

You might not be interested in the whole traceback, but only in the most important information, such as Exception name and Exception message, use:

try:
    with open("not_existing_file.txt", 'r') as text:
        pass
except Exception as exception:
    print("Exception: {}".format(type(exception).__name__))
    print("Exception message: {}".format(exception))

Output:

Exception: FileNotFoundError
Exception message: [Errno 2] No such file or directory: 'not_existing_file.txt'

User · Answer

Python 3  logging  Instead of using the basic print   function  the more flexible logging module can be used to log the exception  The logging module offers a lot extra functionality  e g  logging messages into a given log file  logging messages with timestamps and additional information about where the logging happened   For more information check out the official documentation    Logging an exception can be done with the module-level function logging exception   like so   import logging  try      1 0 except BaseException      logging exception  An exception was thrown      Output   ERROR root An exception was thrown  Traceback  most recent call last     File      Desktop test py   line 4  in  lt module gt      1 0 ZeroDivisionError  division by zero    Notes    the function logging exception   should only be called from an exception handler the logging module should not be used inside a logging handler to avoid a RecursionError  thanks  PrakharPandey      Alternative log-levels  It s also possible to log the exception with another log-level by using the keyword argument exc info True like so   logging debug  An exception was thrown    exc info True  logging info  An exception was thrown    exc info True  logging warning  An exception was thrown    exc info True

User · Answer

One liner error raising can be done with assert statements if that s what you want to do  This will help you write statically fixable code and check errors early   assert type A  is type       requires a string

User · Answer

I was going to leave this as a comment on  jldupont s answer  but I don t have enough reputation    I ve seen answers like  jldupont s answer in other places as well  FWIW  I think it s important to note that this   except Exception as e      print e    will print the error output to sys stdout by default  A more appropriate approach to error handling in general would be   except Exception as e      print e  file sys stderr     Note that you have to import sys for this to work   This way  the error is printed to STDERR instead of STDOUT  which allows for the proper output parsing redirection etc  I understand that the question was strictly about  printing an error   but it seems important to point out the best practice here rather than leave out this detail that could lead to non-standard code for anyone who doesn t eventually learn better   I haven t used the traceback module as in Cat Plus Plus s answer  and maybe that s the best way  but I thought I d throw this out there

User · Answer

For Python 2 6 and later and Python 3 x   except Exception as e  print e    For Python 2 5 and earlier  use   except Exception e  print str e

User · Answer

The traceback module provides methods for formatting and printing exceptions and their tracebacks  e g  this would print exception like the default handler does   import traceback  try      1 0 except Exception      traceback print exc     Output   Traceback  most recent call last     File  C  scripts divide by zero py   line 4  in  lt module gt      1 0 ZeroDivisionError  division by zero

User · Answer

In Python 2 6 or greater it s a bit cleaner   except Exception as e  print e    In older versions it s still quite readable   except Exception  e  print e

User · Answer

In case you want to pass error strings  here is an example from Errors and Exceptions  Python 2 6    gt  gt  gt  try         raise Exception  spam    eggs       except Exception as inst         print type inst        the exception instance        print inst args        arguments stored in  args        print inst               str   allows args to printed directly        x  y   inst              getitem   allows args to be unpacked directly        print  x     x        print  y     y      lt type  exceptions Exception  gt    spam    eggs     spam    eggs   x   spam y   eggs

[python] How to print an exception in Python?

Print/Log the full traceback

Print/log error name/message only

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