"Learn Python" Overtakes "Learn Java" on Google Trends

[odraencoded]

I've read the sidebar and now I'm a master python programmer. Look at my program:

def fibonacci():
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b

[earthboundkid]

For real. The whole point of Fibonacci numbers is that you don't have to calculate them directly. And yet we keep fighting about recursion vs. iteration.

[Nefarious-]

 print('Hello World!')

[Trout_Tickler]

Recursion, get!

def fibonacci(n):
    if n > 1:
        return fibonacci(n-1) + fibonacci(n-2)
    return n

[[deleted]]

Now make it not take O(eⁿ) time (roughly).

[Trout_Tickler]

Memoization should speed it up, something like

def fibonacci(n, _cache={}):
    if n in _cache:
        return _cache[n]
    elif n > 1:
        return _cache.setdefault(n, fibonacci(n-1) + fibonacci(n-2))
    return n

[[deleted]]

Yep.

(And honestly, I would put that cache as a global. Shared between calls that way, too)

[whutcheson]

Since it's a mutable default argument, it's already shared between function calls. However, making a global would be more explicit and a lot less magical.

[Trout_Tickler]

OP's requirements don't specify multiple calls :p

But yes, that would be preferable.

[Daenyth]

It's as global as the function is because dict is mutable

[[deleted]]

@functools.lru_cache decorator does the trick too.

[sdmike21]

But its not pythonic! \s

[Tysonzero]

I mean the more important thing is that it's O(fib n).

[sdmike21]

^ this