decorator101.py

## please run  the following codes in ipython notebook or ipython shell

In [1]: fib = lambda n: 1 if n < 2 else fib(n-1) + fib(n-2)

In [2]: %tiem fib(35)
ERROR: Line magic function `%tiem` not found.

In [3]: %time fib(35)
CPU times: user 3.06 s, sys: 26.7 ms, total: 3.09 s
Wall time: 3.05 s
Out[3]: 14930352

In [4]: def mem(f):
   ...:     res = {}
   ...:     def new_f(n):
   ...:         if n not in res:
   ...:             res[n] = f(n)
   ...:         return res[n]
   ...:     return new_f
   ...: 

In [5]: fib = mem(fib)

In [6]: %time fib(35)
CPU times: user 3.33 ms, sys: 0 ns, total: 3.33 ms
Wall time: 130 µs
Out[6]: 14930352

In [7]: @mem
   ...: def FIB(n):
   ...:     return 1 if n < 2 else FIB(n-1) + FIB(n-2)
   ...: 

In [8]: %time FIB(36)
CPU times: user 3.33 ms, sys: 0 ns, total: 3.33 ms
Wall time: 80.1 µs
Out[8]: 24157817