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

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.

Regards.
0
zljubisic
5/9/2016 7:56:02 PM
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zljubisic@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'}


0
Peter
5/9/2016 8:17:30 PM
On 2016-05-09 20:56, zljubisic@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.
>
The b-prefix is Python-specific. It's not valid JSON syntax.

The JSON format is defined here:

http://www.json.org/

0
MRAB
5/9/2016 8:21:05 PM
zljubisic@gmail.com writes:

> 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?

The result of str(a) is not a valid JSON string.  It starts with a b but
a JSON string must start with a digit of one of -, ", {, [, t, f, n (the
letters being legal only if they are the start of true, false or null.

In fact (in Python 3), passing bytes to str() without an encoding is a
special case -- you get an informal string representation.  I'm not sure
you can be sure what you get though I imagine it's designed to be the
same as Python 2 gave.

> If I set variable a to the
> '{"uuid":"5730e8666ffa02.34177329","error":""}' everything works as
> expected.

That string starts with { so it's OK.  You probably what something like

 json.loads(str(a, 'ascii'))

or maybe 'utf-8' or 'windows-1285' or... well you get the idea.  You
need to say how the bytes should be turned into string characters.

-- 
Ben.
0
Ben
5/9/2016 8:41:48 PM
On 5/9/2016 3:56 PM, zljubisic@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.

This means that the two versions of 'a' are not the same.  So what you 
should have done to debug is print the second to see what you actually 
passed to json.

Editorial: Programming classes should teach basic debugging better. I 
have seen numerous newbie Stackoverflow questions where the person 
should have started with adding a print statement before posting a question.

-- 
Terry Jan Reedy

0
Terry
5/9/2016 11:07:38 PM
On Tue, 10 May 2016 09:07 am, Terry Reedy wrote:

> Editorial: Programming classes should teach basic debugging better. I
> have seen numerous newbie Stackoverflow questions where the person
> should have started with adding a print statement before posting a
> question.

+10000



-- 
Steven

0
Steven
5/10/2016 2:13:03 AM
On Tuesday, May 10, 2016 at 7:43:17 AM UTC+5:30, Steven D'Aprano wrote:
> On Tue, 10 May 2016 09:07 am, Terry Reedy wrote:
> 
> > Editorial: Programming classes should teach basic debugging better. I
> > have seen numerous newbie Stackoverflow questions where the person
> > should have started with adding a print statement before posting a
> > question.
> 
> +10000

Maybe the tutorial should have a small chapter on debugging (introspecting) showing how to use
- print
- type
- dir
And then iterating on these
0
Rustom
5/10/2016 4:22:17 AM
That was it.
Thanks guys for your help.
Best regards.
0
zljubisic
5/10/2016 7:27:50 PM
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