When a program encounters an exception during execution, it is terminated if the exception is not handled. By handling multiple exceptions, a program can respond to different exceptions without terminating it.
try-except blocks can be used to catch and respond to one or multiple exceptions. In cases where a process raises more than one possible exception, they can all be handled using a single
There are several approaches for handling multiple exceptions in Python, the most common of which are discussed below.
Using Same Code Block for Multiple Exceptions
With this approach, the same code block is executed if any of the listed exceptions occurs. Here's an example:
try: name = 'Bob' name += 5 except (NameError, TypeError) as error: print(error) rollbar.report_exc_info()
In the above example, the code in the
except block will be executed if any of the listed exceptions occurs. Running the above code raises a
TypeError, which is handled by the code, producing the following output:
cannot concatenate 'str' and 'int' objects
Using Different Code Blocks for Multiple Exceptions
If some exceptions need to be handled differently, they can be placed in their own
try: name = 'Bob' name += 5 except NameError as ne: # Code to handle NameError print(ne) rollbar.report_exc_info() except TypeError as te: # Code to handle TypeError print(te) rollbar.report_exc_info()
In the above example,
TypeError are two possible exceptions in the code, which are handled differently in their own except blocks.
Investigating Exceptions using If, Elif, Else Statements
Exceptions can also be checked using
if-elif-else conditions, which can be useful if the exception needs to be investigated further:
import errno try: f = open('/opt/tmp/myfile.txt') except IOError as e: rollbar.report_exc_info() if e.errno == errno.ENOENT: print('File not found') elif e.errno == errno.EACCES: print('Permission denied') else: print e
Here, the variable
e holds an instance of the raised
IOError. The additional status code of the exception is checked in the
else blocks and the first match is executed:
File not found
Multiple Except Clauses Matching
There may be cases where a piece of code causes an exception that can match multiple
try: f = open('/opt/tmp/myfile.txt') except EnvironmentError: rollbar.report_exc_info() print('Failed to open file') except IOError: rollbar.report_exc_info() print('File not found')
EnvironmentError is more general than
IOError, it matches the exception in the code above. The EnvironmentError
except clause is listed first, so the code within it gets executed, producing the following output:
Failed to open file
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