[英]Why doesn't finally block return the latest exception when an exception occurs within an except block?
我写了一段代码,我使用回溯来返回异常堆栈跟踪。 但是我忘了导入回溯。
文件名 - trial_main.py
from fastapi import FastAPI
from pydantic import BaseModel
import uvicorn
app = FastAPI()
class RequestJson(BaseModel):
data: str
@app.post("/trial", status_code=200)
async def trial(req:RequestJson):
try:
status = "default"
resp = {
"status": status,
"reason": "default reason"
}
# error point
a = 10/0
status = "complete"
reason = "Finished converting from base64 to image"
resp = {
"status": status,
"reason": reason
}
except Exception as e:
status = "incomplete"
resp = {
"status": status,
"reason": traceback.format_exc(),
}
finally:
return resp
if __name__ == '__main__':
uvicorn.run("trial_main:app", host="0.0.0.0", port=5001, log_level="info")
令我困惑的是,由于找不到回溯模块,为什么代码没有以异常退出。 而是返回之前设置的默认响应。
这是我得到的 API 响应 -
{
"status": "default",
"reason": "default reason"
}
这是我运行 uvicorn 服务器的终端上的 output -
INFO: Started server process [14744]
INFO: Waiting for application startup.
INFO: Application startup complete.
INFO: Uvicorn running on http://0.0.0.0:5001 (Press CTRL+C to quit)
INFO: 127.0.0.1:61809 - "POST /trial HTTP/1.1" 200 OK
Api 端点 -
[POST] http://127.0.0.1:5001/trial
输入重新创建情况 -
{"data": "randomString"}
这里没有发生任何神秘事件。
在 try 块中,您成功地为resp
变量赋值,然后引发异常并执行到 except 块。 您正在尝试为resp
分配新值,但 ImportError 发生在语句的右侧,因此resp
仍然包含旧值,该值将在 finally 块中返回。 异常不会进一步传播,因为 finally 块中有return
,它只是抑制异常。
为了不被 fastapi 样板分散注意力,所有这些都可以用更简单的例子来说明
def always_return():
"""return 1"""
try:
res = 1
raise Exception()
except Exception:
res = 1 / 0
finally:
return res
def never_return():
"""raises ZeroDivisionError"""
try:
res = 1
raise Exception()
except Exception:
res = 1 / 0
finally:
print("finally block exists, but no return here")
return res
>>> print(always_return())
1
>>> print(never_return())
finally block exists, but no return here
ZeroDivisionError: division by zero... traceback
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