[jfischer]

I've personally run into problems when I don't do exact comparisons with True and False. For example, I've forgotten to return a value in one path of a function/method, and then tried to use the result in an if statement in the style recommended by the OP (e.g. if fcall(): do something). After being bitten several times by this, I always do explicit comparisons.

[beagle3]

So you never use "else"? Else is the mother of inexact comparisons.

[jfischer]

In this particular situation, there was no else. I probably added an else clause with an assert return_value == False, as the function call was a virtual dispatch that could have many implementations. Of course, I wouldn't do that for every if/then/else statement in my code. In general, I'd prefer a stricter language that only permitted a boolean as a condition in the IF statement, avoiding this problem altogether.

If you are using truthy/falsey values, I think it can be a code smell that you are not doing enough to catch invalid values up front or should normalize the values closer to their creation point.

[aaren]

Use the else to let you know that something is going wrong, using raise or exit() or some die() function:

    if something:
        do_this()
    elif something_else:
        do_that()
    else:
        # hope we don't end up here
        raise UserWarning('We shouldn't have ended up here')

[beagle3]

But the discussion is about truthy values and inexact comparisons - avoiding inexact comparisons and having an else means:

    if something==True:
        do_this()
    elif something==False:
        do_that()
    else:
        raise UserWarning("Shouldn't be here")

Which is a code smell to me. What I would do is:

    assert isinstance(something, boolean), "Shouldn't happen"
    do_this() if something else do_that()

(replace assert with something else if you want it not to be optimized away with -O; assert is a debug-only construct in Python. Or just drop the assert altogether. In most places, I would - there's no end to the amount of validation you could do, and most of it is unnecessary)