title: In python using while loop calculate circumference and area
body: <p>Write a program that will calculate the circumference and surface area of a circle. Create a table that prints the circumference and surface area for a radius from 1cm to 20 cm inclusive in increments of .5 cm.</p>
  <p>I've tried this</p>
  <pre><code>import math
  
  def main():
  
      # inputs
      radius = int(20)
      i = float
      # loop
      while i in range(1, radius+1):
          a = math.pi * radius ** 2
          c = 2 * math.pi * radius
          print(f'{i:3d}{a:13.2f}{c:15.2f}')
  
          break
  main()
  </code></pre>
  <p>But nothing happens when I run the program.</p>