5(FIVE) Ways for Fibonacci in Python

                                                   5 Ways for Fibonacci in Python

First Method: (use looping)

def fib(n):

 a,b = 1,1

 for i in range(n-1):

  a,b = b,a+b

 return a

print fib(5)

Second Method: (using recursion)

def fibR(n):

 if n==1 or n==2:

  return 1

 return fib(n-1)+fib(n-2)

print fibR(5)

Third Method: (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()

Fourth Method: (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

Fifth Method: (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)