Upload file in flask with other form elements fails with 400 error
It gives an error because you try to access a form field that it cannot find, and assumes that somehow the request was bad, because it didn't include a required form field. You are trying to access:
host = request.form['host-prod-iterator']However you have simply not given it a name in your HTML. If you give it a name, it should work:
<p>Iterator Host : <input type="text" class="form-control" name="host-prod-iterator" id="host-prod-iterator" value="10.47.7.57" required></p>