Boolean to string with lowercase

Question

Can the str.format() method print boolean arguments without capitalized strings?

I cannot use str(myVar).lower() as argument of format, because I want to preserve the case of the letters when myVar is not a boolean.

Please don't post solutions with conditional checks of the values of the variable.

All I am interested is in the possibility of writing the following:

"Bla bla bla {}".format(myVar)

so that the output becomes "Bla bla bla true" when myVar == True and "Bla bla bla false" when myVar == false

Is there a particular reason you want lowercase booleans? Is this [JSON](https://docs.python.org/2/library/json.html)-related, for example? — jonrsharpe, Aug 18 '14 at 10:36
No, `str.format()` will not transform the case of boolean values; you'd need to do so manually. Why do you need this? — Martijn Pieters, Aug 18 '14 at 10:37
@Unihedron: `boolval = 'true' if mybool else 'false'`. Or just `str(mybool).lower()`.. — Martijn Pieters, Aug 18 '14 at 10:40
@MartijnPieters My comment was not intended as an actual solution, just a hint to that the straightforward approach is to conditionally assign string based on boolean. I don't believe there's a library method for this. And it's not too difficult. Also for tubafranz, please take a [tour]. — Unihedron, Aug 18 '14 at 10:41
OK, I just wanted to make sure I have to do it manually. I thought somehow it was possible to "configure" python to have such behaviour, because I wanted to avoid the logic of needed to detect the boolean and perform the lowering of the case. I need this particular behaviour in my code. Anyway, thanks. — tubafranz, Aug 18 '14 at 10:45

score 17 · Answer 1 · answered Aug 18 '14 at 10:45

17

You could use an expression like this

str(myVar).lower() if type(myVar) is bool else myVar

answered Aug 18 '14 at 10:45

John La Rooy

4

`isinstance(myVar, bool)` is preferred, even if `bool` cannot be subclassed further. – Martijn Pieters Aug 18 '14 at 10:50
`str(myVar).lower() if isinstance(myVar, bool) else myVar` – hitautodestruct Apr 26 '22 at 09:02

score 3 · Answer 2 · answered Aug 18 '14 at 11:31

3

Try a lambda that you can call:

>>> f = lambda x: str(x).lower() if isinstance(x, bool) else  x
>>> 'foo {} {}'.format(f(True), f('HELLO'))
'foo true HELLO'

answered Aug 18 '14 at 11:31

Burhan Khalid

2

As recommended in PEP8, better use `def f(x): return str(x).lower() if isinstance(x, bool) else x` instead of lambda https://www.python.org/dev/peps/pep-0008/#programming-recommendations – Touk May 02 '19 at 09:45

2 Answers2