B110: try_except_pass

B110: Test for a pass 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. This is illustrated with the following example

try:
  do_some_stuff()
except Exception:
  pass

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, pass’ 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:

try:
  do_some_stuff()
except ZeroDivisionError:
  pass

Config Options:

try_except_pass:
  check_typed_exception: True

Example:

>> Issue: Try, Except, Pass detected.
   Severity: Low   Confidence: High
   Location: ./examples/try_except_pass.py:4
3        a = 1
4    except:
5        pass

See also

• https://security.openstack.org

New in version 0.13.0.