ERR: catchall exception should be explicity and use Exception EAFP

[immerrr]

EAFP is an acronym that stands for "easier to ask forgiveness than permission" and describes a principle behind the pythonic way of doing some operations that may fail:

try:
    do_smth()
except MyError:
    do_smth_otherwise()

as opposed to

if i_can_do_smth():
    do_smth()
else:
    do_smth_otherwise()

pandas sources use this a lot but often the exception is caught with except: which among other things intercept SystemExit and KeyboardInterrupt. Because of that it's possible that when you're trying to interrupt an operation it goes on simply choosing another code path.

There are valid use cases for carpet-catching excepts like that, most obvious ones being performing some cleanup and re-raising the error afterwards and catching all errors coming from evaluation of user-supplied code. In the rest of the cases except Exception: should be used instead.

[cpcloud]

i think i have a branch lying around somewhere that traverses the entirety of pandas ast and lets you know where carpet bomb exceptions are

[cpcloud]

let me see if i can find it

[cpcloud]

though i suppose

grin 'except:'

is slightly less overkill :)

[cpcloud]

fwiw i would say that even catching Exception should be avoided where possible, since that hides bugs. there are places where pandas uses Exception for control flow, but i bet there are only a handful of those cases and i might argue that even then, being explicit about what your controlling is more clear