Printing "count" of even numbers while-loop with if

Question

I am suppose to be able to complete the following in Python…

Fill in the blanks to complete the function “even_numbers(n)”. This function should count how many even numbers exist in a sequence from 0 to the given “n” number, where 0 counts as an even number. For example, even_numbers(25) should return 13, and even_numbers(6) should return 4.
def even_numbers(n):
   count = 0
   current_number = 0
   while ___ # Complete the while loop condition
       if current_number % 2 == 0::
           ___ # Increment the appropriate variable
       ___ # Increment the appropriate variable
   return count
   
print(even_numbers(25))   # Should print 13
print(even_numbers(144))  # Should print 73
print(even_numbers(1000)) # Should print 501
print(even_numbers(0))    # Should print 1

I’ve tried every variation I can think of for changing every variable I can think of. I have referenced the coursework (I’ve been stuck on this question for a solid week and counting), I have searched Stack Overflow and found multiple variations to reference not exactly what I need to do (and most well advanced from where I am learning right now… even though they solve the problem they don’t…I tried them anyway hoping a light bulb would go off but it hasn’t).

I’ve been trying to get the print(even_numbers(#)) sections to match up… make the script work.

Is there anyone who can explain this to me without giving away the answer outright? I really want to understand where I am going wrong and why. I am a complete novice and mostly self taught from books.

Attempts (a few of them)

def even_numbers(n):
    count = 0
    current_numbers = 0
    while n > current_numbers: # Complete the while loop condition
        if current_numbers % 2 == 0:
            count = count + 1 # Increment the appropriate variable
        else:
            current_numbers = current_numbers + 1 # Increment the appropriate variable
    return count
    
print(even_numbers(25))   # Should print 13
print(even_numbers(144))  # Should print 73
print(even_numbers(1000)) # Should print 501
print(even_numbers(0))    # Should print 1

Evaluation took more than 5 seconds to complete.
                Please try again with a simpler expression.

def even_numbers(n):
    count = 0
    current_number = 0
    while n > current_number: # Complete the while loop condition
        if current_number % 2 == 0:
           count = count + 1 # Increment the appropriate variable
        else:
            current_number = current_number + 1 # Increment the appropriate variable
    return count

print(even_numbers(25))   # Should print 13
print(even_numbers(144))  # Should print 73
print(even_numbers(1000)) # Should print 501
print(even_numbers(0))    # Should print 1

Evaluation took more than 5 seconds to complete.
                Please try again with a simpler expression.

def even_numbers(n):
    count = 0
    current_numbers = 1
    while n > current_numbers: # Complete the while loop condition
        if current_numbers % 2 == 0:
           count = count + 1 # Increment the appropriate variable
           current_numbers = current_numbers + 1
        else:
           current_numbers = current_numbers + 1 # Increment the appropriate variable
    return count
    
print(even_numbers(25))   # Should print 13
print(even_numbers(144))  # Should print 73
print(even_numbers(1000)) # Should print 501
print(even_numbers(0))    # Should print 1

12
71
499
0

Asked By: Brittney Hanna

||

Source

Answer 1

There’s no else: in the code in the assignment. You need to increment current_number every iteration, not just when the number is odd. Otherwise you’ll get stuck on the same number when it’s even. So you should not add an else: block.

Also, the results should count n if it’s even, so the condition should be current_number <= n.

def even_numbers(n):
    count = 0
    current_number = 0
    while current_number <= n: # Complete the while loop condition
        if current_number % 2 == 0::
            count += 1 # Increment the appropriate variable
        current_number += 1 # Increment the appropriate variable
    return count

Answered By: Barmar

Answer 2

I like your last attempt. You need to start current_number at 0 and make sure to use a greater than or equal to sign:

def even_numbers(n):
    count = 0
    current_numbers = 0
    while n >= current_numbers: # Complete the while loop condition
        if current_numbers % 2 == 0:
           count = count + 1 # Increment the appropriate variable
           current_numbers = current_numbers + 1
        else:
           current_numbers = current_numbers + 1 # Increment the appropriate variable
    return count
    
print(even_numbers(25))   # Should print 13
print(even_numbers(144))  # Should print 73
print(even_numbers(1000)) # Should print 501
print(even_numbers(0))    # Should print 1

Answered By: Rojo

Answer 3

You are counting even numbers from current_number == 0 to current_number == n, so you should initialize current_number to 0, and the loop condition should be current_number <= n.

Modifying your third attempt, the code should be:

def even_numbers(n):
    count = 0
    current_number = 0
    while n >= current_number: # Complete the while loop condition
        if current_number % 2 == 0:
           count = count + 1 # Increment the appropriate variable
           current_number = current_number + 1
        else:
           current_number = current_number + 1 # Increment the appropriate variable
    return count
    
print(even_numbers(25))   # Should print 13
print(even_numbers(144))  # Should print 73
print(even_numbers(1000)) # Should print 501
print(even_numbers(0))    # Should print 1

Finally, the current_number = current_number + 1 line is in both if and else branch, so you can extract it out and eliminate else:

def even_numbers(n):
    count = 0
    current_number = 0
    while current_number <= n: # Complete the while loop condition
        if current_number % 2 == 0:
            count += 1 # Increment the appropriate variable
        current_number += 1 # Increment the appropriate variable
    return count

Answered By: NemoYuan2008

Answer 4

This got me the right answer

def even_numbers(n):
   count = 0
   current_number = 0
   while current_number <= n:
       if current_number % 2 == 0:
           count += 1
       current_number += 1
   return count
   
print(even_numbers(25))
print(even_numbers(144))
print(even_numbers(1000))
print(even_numbers(0))

Answered By: Sahan Aloka Mendis

Answer 5

This works, too, and I would absolutely submit this.

def even_numbers(n):
   count = 0
   current_number = 0
   while not current_number: # Complete the while loop condition
       if current_number % 2 == 0:
           count += n // 2 + 1 # Increment the appropriate variable
       current_number = 1 # Increment the appropriate variable
   return count

Answered By: Kelly Bundy

Printing "count" of even numbers while-loop with if

Question:

Answers: