json.loads(...) ValueError: Expecting value: line 1 column 1 (char 0)

[Peter Otten]

zljubisic at gmail.com wrote:

> Hi,
> 
> in python3 my variable looks like this:
> 
> a = b'{"uuid":"5730e8666ffa02.34177329","error":""}'
> str(a) = 'b\'{"uuid":"5730e8666ffa02.34177329","error":""}\''
> 
> If I execute the following command I get the error:
> 
>>>> json.loads(str(a))
> Traceback (most recent call last):
>   File "C:\Program Files (x86)\JetBrains\PyCharm Community Edition
>   2016.1.2\helpers\pydev\_pydevd_bundle\pydevd_exec2.py", line 3, in Exec
>     exec(exp, global_vars, local_vars)
>   File "<input>", line 1, in <module>
>   File "C:\Program Files\Python34\lib\json\__init__.py", line 318, in
>   loads
>     return _default_decoder.decode(s)
>   File "C:\Program Files\Python34\lib\json\decoder.py", line 343, in
>   decode
>     obj, end = self.raw_decode(s, idx=_w(s, 0).end())
>   File "C:\Program Files\Python34\lib\json\decoder.py", line 361, in
>   raw_decode
>     raise ValueError(errmsg("Expecting value", s, err.value)) from None
> ValueError: Expecting value: line 1 column 1 (char 0)
> 
> Why I am getting this error?
> If I set variable a to the '{"uuid":"5730e8666ffa02.34177329","error":""}'
> everything works as expected.

Look at the traceback: "line 1 column 1 (char 0)" mentioned in the error 
message is the leading "b".

When you convert a byte string to unicode with str(bytestr) the "b" prefix 
and the quotation marks are part of the resulting string, but not valid 
JSON. Try a.decode() instead of str(a):

>>> a = b'{"uuid":"5730e8666ffa02.34177329","error":""}'
>>> json.loads(a.decode())
{'error': '', 'uuid': '5730e8666ffa02.34177329'}