Checking the truthfulness of a keyword argument passed to a function does not work as expected - why?

Question

I know how to check if I key in **kwargs exists. Now I want to check the value of an argument passed to a function.

def examplefunc(x,y,**kwargs):

    print(kwargs['extraarg'])
    if 'extraarg' in kwargs == True:
        print(kwargs['extraarg'])
        print("This is not printed")
    
    if 'extraarg' in kwargs: print("This is printed")
    
examplefunc(3,2,extraarg=True)

Output:

True

This is printed

Why isn't This is not printed printed? 'extraarg' in kwargs is false. So why is it proceeding to print This is printed?

I also tried to replace the line if 'extraarg' in kwargs == True with if 'extraarg' == True:, but the output still lacks This is not printed.

chaining operator comparisons... try without `==True` or like this `if '(extraarg' in kwargs) == True` — Jean-François Fabre, Sep 25 '18 at 11:37
@Jean-FrançoisFabre you mean try something like `if ('extraarg' in kwargs)==True`? — toti08, Sep 25 '18 at 11:46
yes, typo when parenthisizing my expr but yes. but just drop `==True` which is just redundant and you never have the issue! — Jean-François Fabre, Sep 25 '18 at 11:48

Sharku · Answer 1 · 2018-09-25T11:54:49.687

-1

def examplefunc(x,y,**kwargs):

    print(kwargs['extraarg'])
    if ('extraarg' in kwargs)==True
        print(kwargs['extraarg'])
        print("This is not printed")

    if 'extraarg' in kwargs: print("This is printed")



if __name__ == "__main__":

    examplefunc(3,2,extraarg=True)

output:

True
True
This is not printed
This is printed

edited Sep 25 '18 at 11:54

answered Sep 25 '18 at 11:33

Sharku

1,052
1
11
24

1

this isn't the question – Jean-François Fabre Sep 25 '18 at 11:37
well, the code does not check that extraarg is True or False – zabop Sep 25 '18 at 11:39
@zabop oh yeah right. I added the check for extraarg == True – Sharku Sep 25 '18 at 11:47
I find it better to use if ('extraarg' in kwargs)==True suggested in the comments on the Q, but otherwise it works, thanks – zabop Sep 25 '18 at 11:51
1

It works because you're not chaining operators! This answer does not explain your issue, it just provides a different solution. @Jean-FrançoisFabre pointed you to the right direction in his comment! – toti08 Sep 25 '18 at 11:53
yep, @Jean-FrançoisFabre's comment is answering my question! – zabop Sep 25 '18 at 12:25

Checking the truthfulness of a keyword argument passed to a function does not work as expected - why?

1 Answers1

output: