equivalent of `a?b:c`

Question

How can I implement this logic more simply?

if isfemale_bit:
    print('F')
else:
    print('M')

The best I have right now is print(['M', 'F'][int(isfemale_bit)]). Is there a better alternative?

No, you need the clearest, most obvious, and most maintainable code possible. Why do you want to emulate an operator that's little better than an obfuscation mechanism? — Nicholas Knight, May 13 '11 at 17:09
I like your original solution but ('M', 'F')[int(isfemale_bit)] is the optimal version. You should be able to give kudos for crafty solutions like yours. — freegnu, May 13 '11 at 17:36
@freegnu: wrong; you should opt for clarity over clever-hackery every time. — Katriel, May 13 '11 at 18:29
Maybe you could take some time out to explain what part of the above statement is unclear. It is easy to read and succinctly performs the desired operation an is valid Python. Maybe I'm reading it wrong. I'm always willing to learn something new. Would you care to back up your opinion and authoritative stance with an example or two where this fails? Or maybe you should take your crusade against succinct code as hackerish witchcraft to the perl section where there is more fuel for the fire. — freegnu, May 17 '11 at 04:46

score 60 · Answer 1 · edited Jan 15 '23 at 07:19

60

In Python 2.5, you can use ternary conditionals like this:

a if b else c

There is more discussion here: Does Python have a ternary conditional operator?

edited Jan 15 '23 at 07:19

Dietrich Epp

205,541
37
345
415

answered May 13 '11 at 17:06

Paul Rosania

9,823
2
20
18

7

This is equivalent to `b?a:c` – Frank Vel Mar 02 '18 at 14:43
@FrankVel If you're referring to the C/C++ expression, then yes. – HelloGoodbye Oct 12 '20 at 20:29
@HelloGoodbye The question title asks about the equivalent of `a?b:c`, which would be `b if a else c`. The order in this answer is different. – Frank Vel Oct 13 '20 at 16:06
1

@FrankVel Sorry, I read your comment a little bit quickly; I thought that was a question. Good point, it's not equivalent to the expression in the question title! – HelloGoodbye Oct 13 '20 at 20:38

score 17 · Answer 2 · answered May 13 '11 at 17:06

17

Ah the ternary operator:

>>> print 'foo' if True else 'bar'
foo
>>> print 'foo' if False else 'bar'
bar

answered May 13 '11 at 17:06

senderle

145,869
36
209
233

score 15 · Answer 3 · answered May 13 '11 at 17:07

15

 print 'F' if isfemale_bit else 'M'

answered May 13 '11 at 17:07

Stefano Borini

138,652
96
297
431

score 9 · Answer 4 · edited Aug 04 '12 at 01:46

9

I guess you are looking for a solution similar o isfemale_bit?'F':'M' in C code So you can use the and-or construction (see Dive Into Python)

print isfemale_bit and 'F' or 'M'

edited Aug 04 '12 at 01:46

Bill the Lizard

398,270
210
566
880

answered May 13 '11 at 17:08

ThibThib

8,010
3
30
37

If `and` evaluates to true, it returns its second argument; `or` returns its last truthy argument. You can combine these properties to get the equivalent of the ternary operator. A little difficult to read, but it works. – Paul Rosania May 13 '11 at 17:19
4

@Paul Rosania, I understand how it works. What I don't understand is why you would do this, ever. – senderle May 13 '11 at 17:27
Learn to think in Python, the whole language, before you poo poo the real syntax of the language. Long winded statements in Python just show the inexperience of the programmer. i.e. You haven't started thinking in Python. – freegnu May 13 '11 at 17:33
@freegnu, I'm not poo-pooing any syntax -- I'm poo-pooing a use case. Are you calling the ternary operator long winded? Are you saying this is a better option? Still, I'll withdraw my snarky question marks -- I was being a bit rude -- sorry! :) – senderle May 13 '11 at 17:51
2

This was common before python had a ternary operator (its fairly new), but no longer really makes sense any more. If you want the ternary to return falsy values, this breaks in a very difficult-to-debug way if you're viewing it as a ternary operator. This is also much more difficult to read than the real ternary. I would advise strongly against it. – Aaron Dufour May 13 '11 at 19:27
Honestly what will you do as the language evolves. Sticking you head in the ground and saying the new language elements are unclear is not helpful. Authoritatively saying the new language elements are unclear, confusing, or unsafe is as ridiculous as it is lame. I'd suggest you learn the new language elements and stop asking others to ignore and shun the perfectly valid, safe, tested, and clearly understandable parts of the language that you may not have been aware of. – freegnu May 17 '11 at 04:29

equivalent of `a?b:c`

4 Answers4