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在py3里同步/异步混合使用 httpx 调用

 1 year ago
source link: https://blog.est.im/2023/stdout-07
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在py3里同步/异步混合使用 httpx 调用

Posted 2023-07-05 | stdout

比如开发需求是请求一个 http API，得到数据，解析一下返回，那么一般的做法是封装一个方法，比如

import httpx


def get_sth(p1, default=MY_VAL):
    # network
    r = httpx.get(API_URL, params={'t1': p1})
    # parsing
    res = r.json().get('my_key') or MY_VAL

但是如果想在 async/await 里用这段代码，就得改成

import httpx


async def get_sth(p1, default=MY_VAL):
    # network
    with http.AsyncClient() as client:
        r = await client.get(API_URL, params={'t1': p1})
    # parsing
    res = r.json().get('my_key') or MY_VAL

注意其中 def get_sth() 也必须改成 async def get_sth 。这就是所谓 async/await 传染性

这个时候，如果你想把这块代码抽象出来，让同步/异步的库都能调用，我在最近重构里找到一个最佳实践：

import httpx


def get_sth(p1, default=MY_VAL):
    r = httpx.Request('GET', API_URL, params={'t1': p1})
    r.parse = lambda x: (x.get('my_key') or MY_VAL)

# 同步调用：
with httpx.Client() as client:
    r = client.send(get_sth())
r.request.parse(r.json())

# 异步调用：
async with httpx.AsyncClient() as client:
    r = await client.send(get_sth())
r.request.parse(r.json())

思路是 逻辑和 transport解耦，也是某种意义上的 Sans-IO 了吧？


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