Why does 1+++2 = 3?

Question

How does Python evaluate the expression 1+++2?

How many ever + I put in between, it is printing 3 as the answer. Please can anyone explain this behavior

And for 1--2 it is printing 3 and for 1---2 it is printing -1

Answer 1

Your expression is the same as:

1+(+(+2)) 

Any numeric expression can be preceded by - to make it negative, or + to do nothing (the option is present for symmetry). With negative signs:

1-(-(2)) = 1-(-2)          = 1+2          = 3 

and

1-(-(-2)) = 1-(2)           = -1 

I see you clarified your question to say that you come from a C background. In Python, there are no increment operators like ++ and -- in C, which was probably the source of your confusion. To increment or decrement a variable i or j in Python use this style:

i += 1 j -= 1 

Answer 2

The extra +'s are not incrementors (like ++a or a++ in c++). They are just showing that the number is positive.

There is no such ++ operator. There is a unary + operator and a unary - operator though. The unary + operator has no effect on its argument. The unary - operator negates its operator or mulitplies it by -1.

+1 

-> 1

++1 

-> 1

This is the same as +(+(1))

   1+++2 

-> 3 Because it's the same as 1 + (+(+(2))

Likewise you can do --1 to mean - (-1) which is +1.

  --1 

-> 1

For completeness there is no * unary opeartor. So *1 is an error. But there is a ** operator which is power of, it takes 2 arguments.

 2**3 

-> 8