Multiply by 2 - Python

Question

The input takes numbers until a negative number is entered, every number before that is multiplied by 2 and the result is printed and formatted to the 2nd digit after the comma. I've tried the following, however the loop just continues endlessly giving me only 1 result, how can I make it stop and multiply with the next input instead?

x = float(input())
while x > 0:
 result = x * 2
 if x < 0:
 print('Negative number!')
 print(f'Result: {result:.2f}')

• khelwood: Where you take input is before the loop, not inside it; so that only happens once.
• user17353495: You can put your input code inside the while loop.
• Barmar: if x < 0: will never be true, because you only go into the loop when x > 0
• Vexarez: I'm also not entirely sure that a while loop should be used, instead of a for
• MFerguson: For loops are better if you want to do something a predetermined amount of times. While loops are better if you want to do something until a condition is met

Answer 1

There are many issues with your code. Here's the fixed version:

while True:
 x = float(input("Input: "))
 if x < 0:
 print('Negative number!')
 break
 else:
 result = x * 2
 print(f'Result: {result:.2f}')

"break" is needed to interrupt the while loop on the first bad result.

• Vexarez: Thank you very much for the detailed answer, I will surely take another look at the loop and fix my mistakes. I was not entirely sure how the entire thing should look like however this has shined some light.