Python Flask 视图返回错误“视图函数没有返回响应”
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Flask view return error "View function did not return a response"
提问by
I have a view that calls a function to get the response. However, it gives the error View function did not return a response. How do I fix this?
我有一个调用函数来获取响应的视图。但是，它给出了错误View function did not return a response。我该如何解决？
from flask import Flask
app = Flask(__name__)
def hello_world():
return 'test'
@app.route('/hello', methods=['GET', 'POST'])
def hello():
hello_world()
if __name__ == '__main__':
app.run(debug=True)
When I try to test it by adding a static value rather than calling the function, it works.
当我尝试通过添加静态值而不是调用函数来测试它时，它起作用了。
@app.route('/hello', methods=['GET', 'POST'])
def hello():
return "test"
采纳答案by Mark Hildreth
The following does not return a response:
以下不返回响应：
@app.route('/hello', methods=['GET', 'POST'])
def hello():
hello_world()
You mean to say...
你的意思是说...
@app.route('/hello', methods=['GET', 'POST'])
def hello():
return hello_world()
Note the addition of returnin this fixed function.
注意return在这个固定函数中的添加。
回答by davidism
No matter what code executes in a view function, the view must return a value that Flask recognizes as a response. If the function doesn't return anything, that's equivalent to returning None, which is not a valid response.
无论在视图函数中执行什么代码，视图都必须返回一个 Flask 识别为响应的值。如果该函数不返回任何内容，则相当于返回None，这不是有效的响应。
In addition to omitting a returnstatement completely, another common error is to only return a response in some cases. If your view has different behavior based on an ifor a try/except, you need to ensure that every branch returns a response.
除了return完全省略语句之外，另一个常见错误是仅在某些情况下返回响应。如果您的视图基于 anif或 a try/具有不同的行为except，则需要确保每个分支都返回响应。
This incorrect example doesn't return a response on GET requests, it needs a return statement after the if:
这个不正确的示例不会返回对 GET 请求的响应，它需要在 之后的 return 语句if：
@app.route("/hello", methods=["GET", "POST"])
def hello():
if request.method == "POST":
return hello_world()
# missing return statement here
This correct example returns a response on success and failure (and logs the failure for debugging):
这个正确的例子返回成功和失败的响应（并记录调试失败）：
@app.route("/hello")
def hello():
try:
return database_hello()
except DatabaseError as e:
app.logger.exception(e)
return "Can't say hello."
