ternary operator with unpacking

[joaomcteixeira]

Hello,
After using ternary operators extensively I am getting lost in this case. It took me a couple of hours to understand why I was getting bugged, and though I've identified the cause I can't understand why this example works like this.

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# pretty clear a = [("1", "2"), ("", "")] b, c = list(zip(*a)) print(b) print(c) ('1', '') ('2', '')

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# here I would expect the same as before, however... a = [("1", "2"), ("", "")] b, c = list(zip(*a)) if True else [""], [""] print(b) print(c) [('1', ''), ('2', '')] ['']

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# this result is expected but why it differs from the second? a = [("1", "2"), ("", "")] b, c = list(zip(*a)) if True else ([""], [""]) print(b) print(c) ('1', '') ('2', '')

Would someone be willing to comment on this?

EDIT: after posting the thread and staring at it, a spark came... ternary operator ended with the comma... so [""] was passed to c even when condition evaluates to True

[buran]

Note that the result of this expression list(zip(*a)) if True else [""] will always be [the result of] first part - list(zip(*a)) because your condition is explicit True, i.e. you are not evaluating the truthfulness of the first part. More over with given value of a the first part will be considered True in any case.

In the second example, on the right hand side you have implicit tuple with first element being list(zip(*a)) if True else [""] and the second element is [""]. During the unpacking they are assigned to b and c respectively.

In the third example the right hand side ultimately ends being list(zip(*a)) - i.e. the first part of the ternary operator as explained at the top of this post. And it's unpacked accordingly into b and c.

[joaomcteixeira]

Yes, the CONDITION being True is just for example. I didn't mean to say I explicitly write True there.
Yes, then I realised that in the ternary expression giving "," ends it and unpacks differently.
I will correct my examples to avoid confusion.

[buran]

Yes, the CONDITION being True is just for example. I didn't mean to say I explicitly write True there.

Sorry, I misunderstood that part

[perfringo]

Just for fun:

Guido van Rossum in Python-Dev list

Pleas stop calling it 'ternary expression'. That doesn't explain
what it means. It's as if we were to refer to the + operator as
'binary expression'

According to PEP308 Python has conditional expression :-)

[joaomcteixeira]

Jeje,
Thanks for sharing the info and the links , let's go for conditional expression.
Best