Why is output 28?? (edited)

Question

class Geom(object):
def __init__(self, h = 10, w = 10):
self.h, self.w = h, w
def rectangle(self):
rect = self.h * 2 + self.w * 2
return rect
a = Geom(4)
print(a.rectangle())

Answer 1

Cryptic Blake,
As you can see in the __init__ magic method, there are 3 parameters <self>, <h> and <w>. But for <h> and <w>, there are default parameter values specified (both set as 10).

When you create a Geom object, you passed only one argument (4) for __init__(). That value will be used for parameter <h>, and since there's only one argument were supplied, <w> will use the default parameter value (10)

So in rectangle() method, self.<h> will be (4) and self.<w> will be (10).

self.h * 2 + self.w * 2
(4) * 2 + (10) * 2
8 + 20

It goes like that I guess ...

Answer 2

cryptic blake

a = Geom(4)

Here a is an instance of class Geom and class Geom has constructor which assign value to h and w

Since Geom has parameter value 4 which will be assign to h but there is no second parameter so 10 (which is default value) will be assign to w

Now rectangle function is called by instance variable a

So self.h * 2 + self.w * 2

Since self.h = 4 and self.w = 10

So finally 4 * 2 + 10 * 2 = 28

Answer 3

Yes.
self.h = 4, self.w = 10
Rect = 4*2 + 10*2 => 8+20 => 28
Returns 28

Answer 4

Ipang I've corrected it thanks🙂

Answer 5

Cryptic Blake,
It should work now after the correction ...

Answer 6

Ipang Can you explain to me why output is 28?

Answer 7

cryptic blake __init__ constructor assigning default values h=10,w=10

a=Geom(4) here,
You are passing 4 so it override h value so h=4, but not given value w so remain w=10. so values now are h=4 , w=10
Remaining in my first post.
Also by others....

try a=Geom(4, 5) then output is 4*2+5*2=18

Answer 8

Cryptic Blake,
Magic method has a couple of underscores wrapping the name.

__init__ # <-- like this ...

Your code had just one underscore wrapping the name ...

* Code had been edited ...

Answer 9

Jayakrishna🇮🇳 And why is that?

Answer 10

a=Geom(4)
python does position matching. So the 4 passed is used to replace h which is the first parameter so h=4 while w remains unchanged as w=10

Answer 11

Hello everyone,
By default you defined the values of h and w each 10.
After you made the instance of the class ( a = Geom(4) ) you changed the value of h from 10 to 4, but you didnt change the value of w, which will remain 10.
So when you call the method ( a.rectangel() ) this method returns rect and rect = 4 * 2 + 10 * 2
When you print it (print(rect) ) the answer is 28