6fib.py

## Example 1: Using looping technique
def fib(n):
 a,b = 1,1
 for i in range(n-1):
  a,b = b,a+b
 return a
print (fib(5))
 
## Example 2: Using recursion
def fibR(n):
 if n==1 or n==2:
  return 1
 return fibR(n-1)+fibR(n-2)
print (fibR(5))
 
## Example 3: Using generators
a,b = 0,1
def fibI():
 global a,b
 while True:
  a,b = b, a+b
  yield a
f=fibI()
f.next()
f.next()
f.next()
f.next()
print (f.next())
 
## Example 4: Using memoization
def memoize(fn, arg):
 memo = {}
 if arg not in memo:
  memo[arg] = fn(arg)
  return memo[arg]
 
## fib() as written in example 1.
fibm = memoize(fib,5)
print (fibm)
 
## Example 5: Using memoization as decorator
class Memoize:
 def __init__(self, fn):
  self.fn = fn
  self.memo = {}
 def __call__(self, arg):
  if arg not in self.memo:
   self.memo[arg] = self.fn(arg)
   return self.memo[arg]
 
@Memoize
def fib(n):
 a,b = 1,1
 for i in range(n-1):
  a,b = b,a+b
 return a
print (fib(5))



def memoize(f):
    memo = {}
    def helper(x):
        if x not in memo:            
            memo[x] = f(x)
        return memo[x]
    return helper
    

def fib(n):
    if n == 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n-1) + fib(n-2)

fib = memoize(fib)

print(fib(40))