-- in Python ? [ Solved ]

Question

One day playing challenges I saw this question :
https://code.sololearn.com/cXwsn5i1JS1Y/?ref=app
I answered it wrong and my opponent too. I thought this is a wrong question but when I ran it, it surprisingly worked with any errors.
Don't know how this '--' syntax came into Python.

Answer 1

-(-5)=5
In languages like C,C++ ,JS ,etc. these are known as decrement/increment operators.

Answer 2

These are the sort of questions that made me realise that Python challenges are a waste of time.
Python promotes readable script.
I can't think of any reason why this concept would be written in a real world code.

Answer 3

Funk You Perhaps, but I think it is the effect as shown by Hima
-(-5)=5
The fact that it was presented as a challenge is detrimental to the coding ideals of Python.
NOTE* My opinion only, and I am often wrong. 😁👍

Answer 4

Funk You Valid point
Thanks for giving me food for thought

Answer 5

Thanks Hima i was convinced "--" did absolutley nothing.

Answer 6

Rik Wittkopp: I think it is not a concept that was coded on purpose, it's rather a 'side effect' of the definition/handling of the operator '-'

Answer 7

If you look at mathematical perspective you are basically multiplying signs with each other.
That means if you have even numbers of minus it will turn to a positive number

Answer 8

Yes I agree Rik Wittkopp, it is exactly this effect. Well I guess they included it into the challenge to 'show' that there is a difference to C/C++ and Java etc...

Answer 9

Rik Wittkopp You're welcome. Thanks for appreciating ^^

Answer 10

Thank you fellows for answering.
As Hima Hima said -(-5)=5
That's why ++a was also giving same answer because : +(+5)=5
It has nothing to do with In/decrement.

Answer 11

Hima
Idk about C and JS, but in C++ such behaviour is the works of unary plus/minus operator.
https://en.cppreference.com/w/cpp/language/operator_arithmetic#Unary_arithmetic_operators

Answer 12

Hima
I was confused
I never knew Python had ++/-- operator
But Thanks to your analysis now I know it's just a nested unary minus operator 😂

Answer 13

Ipang You are correct with your words.
I meant "++/--" are operators which do exist in those languages unlike in python .

Answer 14

Php vs python who is best?

Answer 15

Its just like maths ,even the comments given clarifies that( - plus - equals +) i.e minus plus minus equals plus.
b= --a
b=-(-a) #the minus multiplies the minus in the bracket to give plus
b=a