SystemExit is raised when sys.exit() is called. This exception is expected to propagate up until the
application stops. It is ok to catch it when a clean-up is necessary but it should be raised again immediately.
A bare except: statement, i.e. an
except without any exception class, is equivalent to except BaseException. Both statements will catch every
exception, including SystemExit. It is recommended to catch instead a specific exception. If it is not possible, the exception should be
raised again.
Note that it is also a good idea to reraise the KeyboardInterrupt exception.
This rule raises an issue when a bare except:, an except BaseException or an except SystemExit don’t reraise
the exception caught.
Noncompliant Code Example
try:
open("foo.txt", "r")
except SystemExit: # Noncompliant
pass
except KeyboardInterrupt: # No issue raised but be careful when you do this
pass
try:
open("bar.txt", "r")
except BaseException: # Noncompliant
pass
except: # Noncompliant
pass
Compliant Solution
try:
open("foo.txt", "r")
except SystemExit:
# clean-up
raise
except KeyboardInterrupt:
# clean-up
raise
try:
open("bar.txt", "r")
except BaseException as e:
# clean-up
raise e
except: # Noncompliant
# clean-up
raise
# or use a more specific exception
try:
open("bar.txt", "r")
except FileNotFoundError:
# process the exception
See
