[Tutor] Class

[Alan Gauld]

On 20/06/17 23:39, Rex Florian via Tutor wrote:

> Can someone explain how Python achieves the vector addition of more than 2 vectors
> without some kind of looping?
> 
> class Vector:
>    def __init__(self, a, b):
>    def __str__():
>    def __add__(self,other):
>       return Vector(self.a + other.a, self.b + other.b)

> print(v1 + v2 + v3)

When you do the addition Python evaluates it from left to right
so it is interpreted as:

((v1+v2) + v3)

so Python does:

v1.__add__(v2)

Which returns a new vector, let's call it vt

Python then does:

vt.__add__(v3)

which returns another new vector, lets call it result,
which is what gets printed using

print (result.__str__())


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Alan G
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