title: Python - Writing a function to calculate and return the area of a circle
body: <p>The radius of the circle should be given as an argument to the function and the equation to calculate the area is PI*r2</p>
  
  <pre><code>area = PI*r2
  
  def SetArea (myradius, myarea):
      PI = 3.14159
      myarea = PI*myradius *2
  
      return myarea
  </code></pre>
  
  <p>When I run the programme, the error appears as 'PI is not defined' </p>