斐波那契数列

方法一：不导入任何帮助模块计算数列

FIB = [1]
def fib(n):
    """1 1 2 3 5 8 13 21 34 55"""
    if len(FIB) >= n: return FIB[n - 1]
    return n if n < 2 else (fib(n - 1) + fib(n - 2))


def cache_fib(n):
    fl = len(FIB)
    if fl < n:
        for i in range(fl + 1, n + 1):
            FIB.append(fib(i))
    return FIB[n - 1]

方法二：导入functools模块下的lru_cache方法计算数列

from functools import lru_cache
@lru_cache(maxsize=None)
def fib(n):
    """0 1 1 2 3 5 8 13 21 34 55"""
    return n if n < 2 else fib(n-1) + fib(n-2)