how to clculate the median code example

Example: median

def median(arr):
  
  if len(arr) == 1:
    return arr[0]
    
  else:
    arr = sorted(arr)
    a = arr[0:round(len(arr)/2)]
    b = arr[len(a):len(arr)]
    if len(arr)%2 == 0:
      return (a[len(a)-1]+b[0])/2
    else:
      return a[len(a)-1]