[FIXED] How to write the program that prints out all the positive integer values from 1 up to the input number and each pair of numbers is flipped?

Issue

My code almost works:

number = int(input("Please type in a number: "))
 
a = 2
b = 1
 
while a in range(number) or b in range(number):
    print(a)
    print(b)
    a += 2
    b += 2

with input 6 it works as it should:

Please type in a number: 6
2
1
4
3
6
5

but with input 5 it doesn't and show the sequence 2 1 4 3 instead 2 1 4 3 5

Solution

In the for loop, we are iterating over all the odd numbers up to n (1, 3, 5 ...) and printing the pair of consecutive numbers ( i+1 - even no. first ). As we only wanted numbers up to n to print, we're checking if i+1 is less than or equal to n (p.s. inside for loop the value of i is always less than or equal to n so we just needed to make sure if i+1 matches that condition too ).

n = int(input())
for i in range(1, n+1, 2):
    if i+1 <= n:
        print(i+1)
    print(i)

Answered By - Nick