B112: try_except_continue

B112: Test for a continue in the except block

Errors in Python code bases are typically communicated using Exceptions. An exception object is ‘raised’ in the event of an error and can be ‘caught’ at a later point in the program, typically some error handling or logging action will then be performed.

However, it is possible to catch an exception and silently ignore it while in a loop. This is illustrated with the following example

while keep_going:
  try:
    do_some_stuff()
  except Exception:
    continue

This pattern is considered bad practice in general, but also represents a potential security issue. A larger than normal volume of errors from a service can indicate an attempt is being made to disrupt or interfere with it. Thus errors should, at the very least, be logged.

There are rare situations where it is desirable to suppress errors, but this is typically done with specific exception types, rather than the base Exception class (or no type). To accommodate this, the test may be configured to ignore ‘try, except, continue’ where the exception is typed. For example, the following would not generate a warning if the configuration option checked_typed_exception is set to False:

while keep_going:
  try:
    do_some_stuff()
  except ZeroDivisionError:
    continue

Config Options:

try_except_continue:
  check_typed_exception: True
Example: 
>> Issue: Try, Except, Continue detected.
   Severity: Low   Confidence: High
   Location: ./examples/try_except_continue.py:5
4            a = i
5        except:
6            continue

See also

New in version 1.0.0.