python - Argument Presence Checking via Identity or Boolean Operation? -

when checking method's arguments see whether set, pythonic identity check:

def dothis(arg1, arg2=none):   if arg2 none:     arg2 = myclass() 

or proper form use short-circuiting boolean:

def dothis(arg1, arg2=none):     arg2 = arg2 or myclass() 

in support of former, pep 8 states:

comparisons singletons none should done or not , never equality operators. also, beware of writing if x when mean if x not none -- e.g. when testing whether variable or argument defaults none set other value. other value might have type (such container) false in boolean context!

on other hand, google style guide:

use "implicit" false if @ possible. ...

but @ same time states...

never use == or != compare singletons none. use or not.

does apply "none" since evaluates false always, and/or boolean comparison equivalent ==/!= under hood?

edit: answer last question, "or" doesn't seem equivalent "==" under hood:

in [17]: timeit.timeit("1 or none", number=100000000) out[17]: 2.0310521125793457  in [18]: timeit.timeit("1 none", number=100000000) out[18]: 2.618263006210327  in [19]: timeit.timeit("1 == none", number=100000000) out[19]: 4.554893970489502 

consider happen if arg2 equals "falsish" value such 0 (or empty string, list, tuple, dict or set -- name few).

arg2 = arg2 or myclass() 

would set arg2 myclass() though arg2=0 might have been intended value arg2. always use is determine if arg2 none.