Need solution in python

Question

How the output of this code is 2?

a={0:1, 1:2}
_sum=0
for b in a:
_sum+=b
Print(_sum+b)

Answer 1

When you iterate a dictionary, the loop variable will take the keys.
Inside the loop you are adding all the keys to the _sum variable. That's 0+1=1.
But the variable b will still hold the value of the last key. In this case, 1.
Therefore the total of 2 is printed.

It must be noted, that the iteration order of a dictionary, can change if you modify the dictionary (insert and remove keys), and it even depends on the python version and implementation.
So it is not a good idea to rely on the last key in a serious program (in this case 'b'), at least don't take it for granted.

https://stackoverflow.com/questions/2053021/is-the-order-of-a-python-dictionary-guaranteed-over-iterations

Also in my opinion it is bad coding style to refer to the loop variable outside of the loop's scope, even if it is contextually available.

Answer 2

Try to print b into for loop to understand.
If you want loop dictionnary values :
for b in a.values()