Python开启尾递归优化!

def tail_call_optimized(g): """ This function decorates a function with tail call optimization. It does this by throwing an exception if it is it's own grandparent, and catching such exceptions to fake the tail call optimization. This function fails if the decorated function recurses in a non-tail context. """ def func(*args, **kwargs): f = sys._getframe() # 为什么是grandparent, 函数默认的第一层递归是父调用, # 对于尾递归, 不希望产生新的函数调用(即:祖父调用), # 所以这里抛出异常, 拿到参数, 退出被修饰函数的递归调用栈!(后面有动图分析) if f.f_back and f.f_back.f_back \ and f.f_back.f_back.f_code == f.f_code: # 抛出异常 raise TailRecurseException(args, kwargs) else: while 1: try: return g(*args, **kwargs) except TailRecurseException, e: # 捕获异常, 拿到参数, 退出被修饰函数的递归调用栈 args = e.args kwargs = e.kwargs func.__doc__ = g.__doc__ return func@tail_call_optimizeddef factorial(n, acc=1): "calculate a factorial" if n == 0: return acc return factorial(n-1, n*acc)print factorial(10000)

为了更清晰的展示开启尾递归优化前、后调用栈的变化和tail_call_optimized装饰器抛异常退出递归调用栈的作用, 我这里利用 pudb调试工具 做了动图 <br/>

开启尾递归优化前的调用栈

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