Question

Python 3.7:

Give the following sample code, write the following programs:
• An iterator class called Iteratefirstn that implements __iter__() and __next__() methods where next method should raise an exception for the cur index if it is passed the last element otherwise set cur index to the next index and advance the index by one, i.e. cur, num = num, num+1. Instantiate the class to calculate the sum of 1000000 elements similar to the example.
• Instead of implementing the class, write a generator function that does the same thing.
Sample code:
def firstn(n):
num, nums = 0, []
while num < n:
nums.append(num)
num += 1
return nums
sum_of_first_n = sum(firstn(1000000))  

Answer 1

// FIRST PART OF THE QUESTION 
class Iteratefirstn():

    def __init__(self,N):
        self.N=N
        self.current_value=0

    def __iter__(self):
        return self

    def __next__(self):
        if self.current_value <= self.N:
            current_number=self.current_value
            self.current_value+=1
            return current_number
        else:
            raise StopIteration


obj = Iteratefirstn(10)
sum=0
for num in obj:
    sum+=num
print('Sum = ',sum)

# using generator function

def firstN_generator(N):
    i=0
    while i<=N:
        yield i
        i+=1

sum_of_first_n =0
for num in firstN_generator(1000000):
    sum_of_first_n +=num
print(sum_of_first_n )