Why does program count one extra value (cycle "while")?

Question

Why the program count one more value? For example, I give him N = 50. It gives out:

1
4
9
16
25
36
49
64

Code:

N = int(input())

n = 1
 
k = 1

while n < N:

    n = k ** 2
    print(n)
    k = k + 1

Answer 1

As explained, you're checking n then changing n, you want to change n then check before continuing.

You can use the walrus operator to assign n and check it's value all in the while statement. (requires Python 3.8+)

N = int(input())
n = 1
k = 1

while (n := k**2) < N:
    print(n)
    k += 1

This essentially assigns n to k**2 then checks if that result is <N before continuing.

1
4
9
16
25
36
49

Answer 2

Your program outputs 1 4 9 16 25 36 49 64 if your input is 50 because the `while`` loop is checking the value before you increase it. Once in the loop, you increase it, calculate the square and then print.

If you want it to terminate, try setting calculating n as the last step in the loop:

N = int(input())

n = 1
 
k = 1

while n < N:

    
    print(n)
    k = k + 1
    n = k ** 2