What is the json syntax to insert an item to a list?

Question

I'm trying to insert an item to a list and I keep getting bad request so it's probably because my json is wrong?

Here's what my json looks like:

{  
   "securit_x00e9_":"test",
   "column":"test",
   "__metadata":{  
      "type":"SP.List"
   },
   "numero":"test",
   "Title":"test"
}

securit_x00e9_ it's because I used this letter: é and apparently when I checked the xml it's translated to _x00e9_.

So is this json wrong?

The header and content type is set to application/json; odata: verbose. And I require form digest

MERGE https://mysite/_api/Web/Lists/GetByTitle('myDelphiTestList') HTTP/1.1
Connection: Keep-Alive
Accept: application/json; odata=verbose
If-Match: "5"
User-Agent: Mozarella/1.0 (compatible; Indy Library)
X-RequestDigest: 0x7E78B662646D13B263E3B9964C4D5554F0795C67CB99EFB37D7BA8FB2997DB1D748634497241F0F0BDA1AFF887971D1D2CF98E0739AF5E0969D201AEA834BBE2,28 Jul 2016 09:12:52 -0000
Content-Length: 79
Host: mysite
Authorization: Basic eW91cmljdFw2MDEyNzA4NjY6RGV0cm9pdCUxNTM0Mg==

{"column":"test","__metadata":{"type":"SP.List"},"numero":"test","Title":"tes"}

Answer 1

Your JSON for updating list item should be like this.

{ 
"__metadata":{ "type":"SP.Data.YourListNameListItem"},
"securit_x00e9_":"test",
"column":"test",   
"numero":"test",
"Title":"test"
}

In type you must write "SP.YourListNameListItem"

Update-1:

Try removing securit_x00e9_":"test" line from your JSON, if its update then you have to try the JSON as

 { 
    "__metadata":{ "type":"SP.Data.YourListNameListItem"},
    "_x00e9_":"test",
    "column":"test",   
    "numero":"test",
    "Title":"test"
    }

Update-2 :

Based on your commented error message

"The given key was not present in the dictionary"

Your headers should look like this

headers = {'X-RequestDigest': token,
           'Accept': 'application/json; odata=verbose',
           'Content-Type': 'application/json; odata=verbose',
           'Content-Length': lengthofbody}

We can avoid 'Content-Length' header. I tried without this header, It worked.

source

Update-3:

Please ensure that your url should be like

https://mysite/_api/Web/Lists/GetByTitle('myDelphiTestList')/items(YourItemID)

Also your HTTP Methods should be POST