CODEWITHSUNDEEP
pythontrackingmemoization
RockyS
RockyS

Reputation: 59

Memoization and Function Tracking

I am trying to track how many times a function is run, as well as use memoization to avoid needlessly running the function. I cannot figure out why, but it seems that memoization is storing two of the same value for most values. 

def track(f):
  def wrapper(arg):
    wrapper.count += 1
    print(arg)
    return f(arg)
  wrapper.count = 0
  return wrapper

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

@track
@memoize
def fib(n):
  return n if n in (0,1) else fib(n-1) + fib(n-2)

print('Result:', fib(10), '\nCount:', fib.count)

The results should be coming out as

10
9
8
7
6
5
4
3
2
1
0
Result: 55
Count: 11

For some reason, it is giving off double for everything less than 9. Count is actually returning 19. Any help would be greatly appreciated.

Upvotes: 2

Views: 75

Answers (1)

Vadim Shkaberda
Vadim Shkaberda

Reputation: 2936

You need to to move memoize into track:

def track(f):
  @memoize
  def wrapper(arg):
    wrapper.count += 1
    print(arg, end=' ')
    return f(arg)
  wrapper.count = 0
  return wrapper

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

@track
def fib(n):
    return n if n in (0,1) else fib(n-1) + fib(n-2)

print('Result:', fib(10), '\nCount:', fib.count)
10 9 8 7 6 5 4 3 2 1 0 Result: 55 
Count: 11

By adding additional argument to a track you could control if you want to use memoize decorator. In this case you should use functools.wraps :

from functools import wraps

def track(is_memoized):
  def dec(f):
    def wrapper(arg):
      wrapper.count += 1
      print(arg, end=' ')
      return f(arg)
    wrapper.count = 0
    if is_memoized:
      wrapper = memoize(wrapper)
    return wrapper
  return dec

def memoize(f):
    memo = {}
    @wraps(f)
    def wrapper(arg):
        if arg not in memo:            
            memo[arg] = f(arg)
        return memo[arg]
    return wrapper


@track(is_memoized=True)
def fib(n):
    return n if n in (0,1) else fib(n-1) + fib(n-2)

print('Result:', fib(10), '\nCount:', fib.count)
10 9 8 7 6 5 4 3 2 1 0 Result: 55 
Count: 11

@track(is_memoized=False)
def fib(n):
    return n if n in (0,1) else fib(n-1) + fib(n-2)

print('Result:', fib(5), '\nCount:', fib.count)
5 4 3 2 1 0 1 2 1 0 3 2 1 0 1 Result: 5 
Count: 15

Upvotes: 1

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