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 24.186946153640747 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可快速缩小fib()函数的参数值，极大效率地减少fib函数的递归次数： 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)。如设置的位数不够会报错：ValueError: Exceeds the limit (10000 digits) for integer string conversion; use sys.set_int_max_str_digits() to increase the limit
