FastAPI 405 method not allowed when creating forms in html

Question

I created a tool in flask, but want to move it to fastapi. I defined two routes as follows:

from fastapi import FastAPI, Request, Form
from fastapi.templating import Jinja2Templates
from fastapi.responses import HTMLResponse


@app.get("/mytool")
async def home(request: Request, response_class=HTMLResponse):
    # displays tool 
    return templates.TemplateResponse("index_tool.html", {"request": request})


@app.post("/mytool")
async def home(request: Request, 
               var1: str = Form(), 
               var2: str = Form(), 
               var3: int = Form(), 
               var4: int = Form()):

    # ... perform calculation 
    result = myCalculation(var1, var2, var3, var4)
    return templates.TemplateResponse("index_tool.html", {"request": request, 
                                                          "result": result})

However, whenever I submit the form. It gives the error POST / HTTP/1.1" 405 Method Not Allowed, even though I defined both the GET and POST route. How should I go about creating such a tool?

MatsLindh · Accepted Answer · 2022-09-09 20:19:07Z

2

There's a few issues. You're using the same method name (home) for both the post and the get endpoint - this will make it hard to use url_for in your templates to get the actual endpoint from a route name.

Your POST in the log is against /, not against /mytool which is the path you've registered in your code.

POST / HTTP/1.1" 405 Method Not Allowed
     ^

vs

@app.post("/mytool")
           ^^^^^^^

Since you haven't included your actual template where the form element defines where the submission should be sent, you should probably replace it with something like:

<form method="post">

.. if the URL is the same, or if you fix the function names, you can do:

<form method="post" action="{{ url_for('home_calculate') }}">

answered Sep 9, 2022 at 20:19

MatsLindh

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1 Comment

Jeroen Vermunt Over a year ago

silly me, it was caused by the same method name. Too busy looking for problems elsewhere.

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