[Tutor] A question about daunting KeyError

[Steven D'Aprano]

Hi Taishi, and welcome.

On Wed, Jul 24, 2019 at 03:21:03AM +0000, TAISHI KAWAMURA wrote:

[...]
> I'm suspecting that Anaconda might keep raising the error, or simply 
> there are bugs in the codes. However, I can't be sure what the real 
> cause is.

Almost certainly it will be a bug in your code, or unexpected values in 
your data. It is possible that it is a bug in Anaconda, but not very 
likely.

Start by removing Anaconda from the problem: what happens if you run 
your code using the plain Python interpreter, without Anaconda involved? 
>From the operating system command line, run something like this:

    # Windows CMD.EXE
    py path/to/myscript.py

    # Linux or Mac OS shell
    python path/to/myscript.py


Of course the example command you run will depend on the version of 
Python you are using, and the name and path to your script.

If the error goes away without Anaconda involved, then it is *possible* 
that it is a bug in Anaconda. But I expect the error will remain.

Then show us the full traceback of the error. Copy and paste the FULL 
exception message, starting with the line "Traceback" and ending with 
the KeyError and error message, something like this but probably longer:

    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    KeyError: (1, 2, 3)


Once you know the line where the error is occurring, you could introduce 
some debugging code:

    try:
        result = data[key]
    except KeyError:
        log(data)
        log(key)
        raise


or use the debugger to investigate why the key is missing.

You should also read this:

http://sscce.org/


It is written for Java programmers, but it applies to Python too.




-- 
Steven