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python - 有没有办法在异步 python 中等待值

问题描述

基本上我正在尝试在 Python 中使用异步代码。一开始，我想我会做一个斐波那契计算器。但我无法使用它，这是我的代码

import asyncio as a
cache = {}

async def fib(n):

    if n < 10:
        a.sleep(0.001)
    else:
        if n in cache:
            result = cache[n]
        else:
            result = await fib(n - 2) + await fib(n - 1)
    cache[n] = result
    return result

async def main():
    res = await fib(100)
    print(res)

a.run(main())

我得到的错误是

Warning (from warnings module):
  File "<pyshell#3>", line 4
RuntimeWarning: coroutine 'sleep' was never awaited
Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    a.run(main())
  File "C:\Users\Owner\AppData\Local\Programs\Python\Python38-32\lib\asyncio\runners.py", line 43, in run
    return loop.run_until_complete(main)
  File "C:\Users\Owner\AppData\Local\Programs\Python\Python38-32\lib\asyncio\base_events.py", line 616, in run_until_complete
    return future.result()
  File "<pyshell#5>", line 2, in main
    res = await fib(100)
  File "<pyshell#3>", line 9, in fib
    result = await fib(n - 2) + await fib(n - 1)
  File "<pyshell#3>", line 9, in fib
    result = await fib(n - 2) + await fib(n - 1)
  File "<pyshell#3>", line 9, in fib
    result = await fib(n - 2) + await fib(n - 1)
  [Previous line repeated 43 more times]
  File "<pyshell#3>", line 11, in fib
    return result
UnboundLocalError: local variable 'result' referenced before assignment

谢谢。

标签： pythonpython-3.xasync-awaitpython-asyncio

解决方案

你错过了初始化值。它们被预先添加到下面的缓存中：

import asyncio as a
cache = {0: 0, 1: 1}

async def fib(n):
    if n in cache:
        result = cache[n]
    else:
        result = await fib(n - 2) + await fib(n - 1)
    cache[n] = result
    return result

async def main():
    res = await fib(100)
    print(res)

a.run(main())

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