Why it gives wrong output

Question

print(1+99+1-100/2*4) I want output 2 but it gives -99.0

Answer 1

That's why parentheses and order of operations are so important.... :)

print(1+99+1-100/2*4)
1+99+1 = 101
100/2*4 = 200
101 - 200 = -99

So the output is actually correct :)

And just to nitpick a little @visph :) - x/2*4 is not always x*2 :)

>>> 5/2*4
8

In python2, the slash operator performs integer division. Which leads to this ugly and confusing result. So it was changed in python3:

>>> 5/2*4
10.0

Answer 2

@Bogdan:

I cannot give you wrong...

It's a trap, so your information is certainly useful for many users here (even for me: I wasn't remember that in C++ (I just pseudo learned C# here, so not surprising if I don't also remember for it) the division was integer by default... and while I write it I understand my mistake: this isn't a default behaviour, this is a context behaviour, as in every language with hard typed variable: expected result is integer as variable type is declared as integer, so integer division is relatively logically applied ^^ but this is an explicit context ;P )

Answer 3

@Bogdan: integer division is a special case, not really related to this context, as Py3 is used (and teached) on Sololearn ;) (without specification, I read a mathematical expression, so working in decimal, not integer)

Answer 4

:D

I love this kind of expression: num/2*4...
... wich could easily be reduce to: num*2 :P

Answer 5

Your code is incorrect

print(1+99-49/2*4) //output 2.0

Answer 6

print(1+99-49/2*4)
// 1+99=100
//49/2=24.5 * 4 = 98
// 100 -98 = 2

Answer 7

@visph - ok, python2 is not taught on SoloLearn. Then how about C++ or C#? :)

int main() {
int a = (5/2)*2;
cout<<a;
return 0;
}

Or:

static void Main(string[] args)
{
int a = (5/2)*2;
Console.WriteLine(a);
}

They both print "4".

I agree with you that mathematically speaking, x/2*4 = x*2 . I'm just pointing out these "strange behaviours" so that people know of them and are not surprised when they first encounter them :)

Answer 8

Can you explain your answer?