json.decode, error: expected value but found invalid token at character 1

[WillyBumBum 0]

I am trying, to read out a json which came from some motor.

 

In the virtual device I can fetch the json and when I debug it looks quit normal -> json_incoming [{"Actief" : 45, "Stand": 1}]

but when I try to decode the json it just gave an error which I don't really understand: expected value but found invalid token at character 1

 

I attached the main loop and the debugwindow.

 

Does anybody know how to fix this error?

 

 

Many thanks!

 

 

 

 

 

 

 

 

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[petergebruers 1,268]

Don't know and unfortunatley I have a few things to do first, but I find this question intriguing enough to do a quick test:

 

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It does a round trip decode encode and it works. So it prints:

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Maybe your data contains extra, unprintable characters? Can you please print the length of the response string?

[WillyBumBum 0]

Thank you for your fast response.

 

I put the incoming "response" string into the function string.len and it has a length of 28.

[petergebruers 1,268]

That's odd, I count 29 in my example. So your response can't be identical. If it's whitespace it doesn't matter. Can you spot the difference? Or... Is my example wrong?

[WillyBumBum 0]

the diffrence is a space just before the colon, of "Actief".

So in my view the string length is correct.

[petergebruers 1,268]

OK then. I'm thinking aloud here... would it be possible to dump the ascii code of each character? I don't have code at hand but I can have a look at it later. And, what does print(type(X)) say (X is your json string or response variable)?

[WillyBumBum 0]

I find the solution and figured out what the problem was. There are two ways to solve this problem

response=incoming json

JsonTable=decoded json.

 

1:

JsonTable=json.decode(tostring(response)). # some how this translates the json to be interpretable for the json.decode function, probably the json.decode function doesn't understand UTF8

 

2:

JsonTable=json.decode(response) # In this case I could force the json encoding in the motor to be written as ASCII instead of UTF8. The ASCII JSON string doesn't cause any trouble with the json.decode() function.

 

Anyway, thank you for your help, I appreciated that

[petergebruers 1,268]

Glad it's solved! I'm unsure about the explanation, UTF-8 is the default encoding, but I don't think I've ever had a HC2 related JSON file that contained non-ascii data. So I don't know.

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[perjar 10]

On ‎2016‎-‎04‎-‎12 at 3:09 PM, WillyBumBum said:

I find the solution and figured out what the problem was. There are two ways to solve this problem

response=incoming json

JsonTable=decoded json.

 

1:

JsonTable=json.decode(tostring(response)). # some how this translates the json to be interpretable for the json.decode function, probably the json.decode function doesn't understand UTF8

 

2:

JsonTable=json.decode(response) # In this case I could force the json encoding in the motor to be written as ASCII instead of UTF8. The ASCII JSON string doesn't cause any trouble with the json.decode() function.

 

Anyway, thank you for your help, I appreciated that

 

I am having the same issue. Tried your recipe #1 above and it worked for a while but now I am back to square one again. 

 

Has anyone else encountered this problem and found away to fix it?

 

[perjar 10]

On 2018-03-05 at 7:21 PM, perjar said:

 

I am having the same issue. Tried your recipe #1 above and it worked for a while but now I am back to square one again. 

 

Has anyone else encountered this problem and found away to fix it?

 

 

Update: It turned out that the problem I had was that the REST interface I was calling returned an error message which caused json.decode to malfunction. 

Problem fixed by not calling json.decode if there is an error from the request.