fib.py

class DynamicFib:
  def __init__(self):
    self.memo = {0: 0, 1: 1}
  
  def fib(self, n):
    if n not in self.memo:
      self.memo[n] = self.fib(n-1) + self.fib(n-2)
    return self.memo[n]

def slow_fib(n):
  if n <= 1:
    return n
  return slow_fib(n-1) + slow_fib(n-2)
  
fib = DynamicFib()
fib.fib(30)  # 57 microseconds wall time
slow_fib(30)  # 434 milliseconds wall time