Python Program to Print Even Numbers from 1 to n

You can print even numbers from 1 to n in Python using a for loop and the condition if i % 2 == 0, like this: for i in range(1, n+1): if i % 2 == 0: print(i).

Examples

Input5

Output2 4

Input10

Output2 4 6 8 10

Input1

Output

How to Think About It

To print even numbers from 1 to n, think about checking each number in this range to see if it divides evenly by 2. If it does, it is even and should be printed. We start from 1 and go up to n, testing each number with the % operator to find the remainder when divided by 2. If the remainder is zero, the number is even.

Algorithm

1

Get the input number n.

2

Start a loop from 1 to n inclusive.

3

For each number, check if it is divisible by 2 (remainder zero).

4

If yes, print the number.

5

End the loop after reaching n.

Code

python

n = int(input("Enter the value of n: "))
for i in range(1, n + 1):
    if i % 2 == 0:
        print(i)

Output

Enter the value of n: 10
2
4
6
8
10

Dry Run

Let's trace the program with input n = 5 to see how it prints even numbers.

1

Input

User enters n = 5

2

Loop start

i starts at 1

3

Check if i is even

1 % 2 = 1 (not zero), so skip printing

4

Next i

i = 2, 2 % 2 = 0, print 2

5

Continue loop

i = 3, 3 % 2 = 1, skip; i = 4, 4 % 2 = 0, print 4; i = 5, 5 % 2 = 1, skip

6

Loop ends

All numbers checked up to 5

i	i % 2	Print?
1	1	No
2	0	Yes (2)
3	1	No
4	0	Yes (4)
5	1	No

Why This Works

Step 1: Loop through numbers

The program uses a for loop to go through every number from 1 to n.

Step 2: Check even condition

It uses i % 2 == 0 to check if the number is even, meaning no remainder when divided by 2.

Step 3: Print even numbers

If the condition is true, it prints the number, so only even numbers appear in the output.

Alternative Approaches

Using range with step 2 starting from 2

python

n = int(input("Enter the value of n: "))
for i in range(2, n + 1, 2):
    print(i)

This method is more efficient because it only loops through even numbers directly.

Using list comprehension and join

python

n = int(input("Enter the value of n: "))
evens = [str(i) for i in range(1, n + 1) if i % 2 == 0]
print('\n'.join(evens))

This creates a list of even numbers first, then prints them all at once.

Complexity: O(n) time, O(1) space

Time Complexity

The program checks each number from 1 to n once, so it runs in linear time O(n).

Space Complexity

It uses constant extra space O(1) because it prints numbers directly without storing them.

Which Approach is Fastest?

Using range(2, n+1, 2) is faster because it skips odd numbers, reducing loop iterations by half.

Approach	Time	Space	Best For
Check each number with % 2	O(n)	O(1)	Simple and clear logic
Range with step 2	O(n/2)	O(1)	More efficient looping
List comprehension	O(n)	O(n)	When you need a list of even numbers