异步编程

异步计算斐波那契数列，半分钟可以计算出第5000万项的数值。

完整代码

import sys, time, asyncio
def timer(func):  
    def wrapper(*args, **kwargs):  
        start_time = time.time()  
        result = func(*args, **kwargs)  
        end_time = time.time()  
        print(f"{func.__name__} took {end_time - start_time} seconds to run.")  
        return result  
    return wrapper
def fib(n):
    if n<600:
        n1 = n2 = 1
        for _ in range(2,n):
            n1,n2 = n1+n2,n1
        return n1
    t = n//2
    if n%2:
        return fib(t+1)**2 + fib(t)**2
    else:
        return fib(t+1)**2 - fib(t-1)**2
@timer
def Fib(n):
    return fib(n)
async def asyncFib(n):
    res = Fib(n)
    print(res)
async def main():
    await asyncio.gather(*tasks)
if __name__ == "__main__":
    sys.set_int_max_str_digits(0)
    parms = [5000_0000, 2000_0000, 1000_0000]
    tasks = [asyncFib(p) for p in parms]
    loop = asyncio.run(main())

输出结果

Fib took 29.4418728351593 seconds to run.

Squeezed text(121505 lines).

Fib took 5.968385457992554 seconds to run.

Squeezed text(121505 lines).

Fib took 2.031674385070801 seconds to run.

Squeezed text(121505 lines).

Fib took 0.0 seconds to run.

33644764876431783266621612005107543310302148460680063906564769974680081442166662368155595513633734025582065332680836159373734790483865268263040892463056431887354544369559827491606602099884183933864652731300088830269235673613135117579297437854413752130520504347701602264758318906527890855154366159582987279682987510631200575428783453215515103870818298969791613127856265033195487140214287532698187962046936097879900350962302291026368131493195275630227837628441540360584402572114334961180023091208287046088923962328835461505776583271252546093591128203925285393434620904245248929403901706233888991085841065183173360437470737908552631764325733993712871937587746897479926305837065742830161637408969178426378624212835258112820516370298089332099905707920064367426202389783111470054074998459250360633560933883831923386783056136435351892133279732908133732642652633989763922723407882928177953580570993691049175470808931841056146322338217465637321248226383092103297701648054726243842374862411453093812206564914032751086643394517512161526545361333111314042436854805106765843493523836959653428071768775328348234345557366719731392746273629108210679280784718035329131176778924659089938635459327894523777674406192240337638674004021330343297496902028328145933418826817683893072003634795623117103101291953169794607632737589253530772552375943788434504067715555779056450443016640119462580972216729758615026968443146952034614932291105970676243268515992834709891284706740862008587135016260312071903172086094081298321581077282076353186624611278245537208532365305775956430072517744315051539600905168603220349163222640885248852433158051534849622434848299380905070483482449327453732624567755879089187190803662058009594743150052402532709746995318770724376825907419939632265984147498193609285223945039707165443156421328157688908058783183404917434556270520223564846495196112460268313970975069382648706613264507665074611512677522748621598642530711298441182622661057163515069260029861704945425047491378115154139941550671256271197133252763631939606902895650288268608362241082050562430701794976171121233066073310059947366875

代码分析

耗时装饰器

def timer(func):  

   def wrapper(*args, **kwargs):  

       start_time = time.time()  

       result = func(*args, **kwargs)  

       end_time = time.time()  

       print(f"{func.__name__} took {end_time - start_time} seconds to run.")  

       return result  

   return wrapper

@timer

def Fib(n):

   return fib(n)

斐波那契数列

def fib(n):

   if n<600:

       n1 = n2 = 1

       for _ in range(2,n):

           n1,n2 = n1+n2,n1

       return n1

   t = n//2

   if n%2:

       return fib(t+1)**2 + fib(t)**2

   else:

       return fib(t+1)**2 - fib(t-1)**2

使用以下两个恒等式快速缩小fib()函数参数n的量级，极速减少函数递归的次数：

fib(2*t+1)=fib(t+1)**2 + fib(t)**2

fib(2*t)=fib(t+1)**2 - fib(t-1)**2

异步函数

async def asyncFib(n):

   res = Fib(n)

   print(res)

async def main():

   await asyncio.gather(*tasks)

设置字串处理的最大位数

sys.set_int_max_str_digits(0)

新版python默认只能最大处理4300位的字串，参数为0即解除长度限制。也可以设置具体数据为限制最长长度，比如sys.set_int_max_str_digits(10000)，注意本例中fib(5000_0000)的值有几千万位，需要设置1亿位sys.set_int_max_str_digits(1_0000_0000)。