Flake8 Not Recognizing built-in exception
Running python 2.7.8
I get the follwoing:
except FileNotFoundError:
NameError: name 'FileNotFoundError' is not defined
If I change to OSError
it works correctly on python 3
except OSError:
FileNotFoundError is a subclass of OSError
in python3
Using OSError
will catch more than just the FileNotFound
error in python 3 so you may want to add additional checks.
For python 2
it is an IOError
:
You can catch the specific error:
import __builtin__
exc = getattr(__builtin__,"IOError","FileNotFoundError")
try:
(open("bad_file"))
except exc:
pass
Sure there are betters ways but for python 3:
try:
f = (open("bad_file"))
except OSError as e:
if isinstance(e, FileNotFoundError):
pass
else:
raise e
I found a couple of mentions of this issue on the Python Code Quality tools repo. Specifically Issue #75.
Two workarounds were listed. You can use the --builtins
flag to specify a comma separated list of known builtins that flake8 is flagging.
$ flake8 example.py
example.py:3:8: F821 undefined name 'FileNotFoundError'
$ flake8 --builtins=FileNotFoundError,... example.py
$
The other workaround is running flake8 under python3 instead of python2.
$ /usr/bin/python3.5 -m pyflakes example.py
$
Hopefully one of these two solutions will work out for you, as twisting your code up to work around a syntax check tool is counterproductive.