Matthew Moisen Matthew Moisen - 2 months ago 49
Python Question

How to intentionally cause a 400 Bad Request in Python/Flask?

A consumer of my REST API says that on occasion I am returning a

400 Bad Request
-
The request sent by the client was syntactically incorrect.
error.

My application (Python/Flask) logs don't seem to be capturing this, and neither do my webserver/Nginx logs.

Edit: I would like to try to cause a 400 bad request in Flask for debugging purposes. How can I do this?

Following James advice, I added something similar to the following:

@app.route('/badrequest400)
def bad_request():
return abort(400)


When I call this, flask returns the following HTML, which doesn't use the "The request sent by the client was syntactically incorrect" line:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<title>400 Bad Request</title>
<h1>Bad Request</h1>
<p>The browser (or proxy) sent a request that this server could not understand.</p>


(I'm not sure why it isn't including the
<body>
tags.

It appears to me that there are different variations of the 400 error message. For example, if I set a cookie to a value of length 50,000 (using Interceptor with Postman), I'll get the following error from Flask instead:

<html>
<head>
<title>Bad Request</title>
</head>
<body>
<h1>
<p>Bad Request</p>
</h1>
Error parsing headers: 'limit request headers fields size'

</body>
</html>


Is there a way to get Flask to through the different variations of 400 errors?

Answer Source

Why don't you define a URL route that simply throws an HTTP/400 error?

@app.route('/badrequest400)
def bad_request():
    return abort(400)